Going to break this down by each segment to give you a proper answer to this. But if you want a TL;DR...
The game isn't finished, this isn't a beta or an alpha it's a staple everything together, get the main story events working properly then go back to the beginning and start trimming and cleaning up. Money is tight but I spend what I can into it.
So don't complain about a game that isn't finished, or complain about a game that just isn't your taste.
With that said, let me break down each section in more detail.
"Gameplay Loop"
The gameplay loop isn't finished, many elements haven't been added yet either. The reason the areas are large in Trighbon is the first boss would chase you around the area similar to Ao oni but that got pushed back to the final release as I just wanted to get the basic story beats done. The save issue was brought up before and I already know of it.
"Got one shot"
The spider boss is one of the easier in the game. The reason you got one shot is either: It hit you when the sprites were active or you didn't have enough HP to survive his basic attacks.
One part of gameplay here is exploring and gathering materials + herbs you find in the environment, another is building armor to reduce damage taken. The armor needs buffed and more sets need added, which is being worked on. Again the one shot or high damage issue has already been addressed and being worked on.
"Inspiration"
Resident Evil 4 was one inspiration but not my main one. If I said what the main inspiration was it would be obvious what your fighting so I don't want to spoil that. Having the van move sounds like a good idea on paper but there's not much tension when you have a safe area and save spot you can go to regularly. A few new saves were added and some are being planned and there is a journal system that's being worked on and it will give you basic directions of where to go I just haven't finished it yet.
"Move the Van?"
Completion of certain parts to move the van happens in a few select areas already. The other saves are near the salesman or book trader in select areas only.
"Terrible Dialogue"
Dialogue was already planned to be reworked but it's not as bad as your making it out to be. Most dialogue will be the same as the beginning conversations with Abby and Shane where you can just choose to progress story instead of listening to it all, but you didn't bring this up for some reason? Not sure if you thought it was mandatory but I can tell you it's not.
Books are primarily for trading to the book trader for rare items. There is no exposition dumping in books because the "lore" in those books is optional and not important to the main story of this game, just an optional read for those who care.
Ignoring the "show don't tell" section. Games not finished, NPCs have already been made to the town and just need to be added. Again, games not finished not even in alpha.
"Detective Apprentice"
Glad you noticed the detective apprentice is arrogant and only in it for the money and entertainment. Almost like he was given the job by family and only looking to get a paycheck. This was partially explained in some dialogue but you either skipped over it or it wasn't implemented. I would need to go back and look to make sure.
"Game doesn't explain itself"
I already know the game doesn't explain much, this complaint was made before and I answered this further up when I said games not finished, just trying to get main story beats done before additions,trimming and polishing.
"Generic Sandbox"
The game is focused on exploration, when entering a new area you are told to explore to see what you can find, your even told this in the intro area. So yes wandering/exploring the area is part of the game. Your also told EXACTLY which buildings to go to or which direction to go during briefing, the only problem is in Trighbon where the one house door is locked for no real reason, I need to leave it unlocked so people can go straight to the mansion if they really choose to. If you don't like these types of games that's one thing, but don't claim it's a problem when multiple times you are told to explore your surroundings. On top of skipping dialogue I'm not surprised you got lost or stuck.
You don't have to check every area. I can only think of one key that is under a table with no real explanation but that key was moved in 0.8 which isn't ready yet.
"Bunch of random experiment systems"
Wrong, I wanted to make a shooter game with puzzle elements which is what I'm making. I chose to make a shooter after seeing an older game use it and I knew it'd be fun to make one and RPGM is the easiest engine to use and the only engine I know how to work with.
"Just some addict dude"
Wrong. You missed an event explaining that, you'll find him again in the slums area and he tells you something interesting that I won't spoil here for others who may read this.
"Zombie?"
Nope. Not a zombie, won't spoil what it is but it hasn't been explained well in the story as the dialogue needs reworked as stated above. A majority of enemies in the game have red eyes but it's hard to see with the pixel art and areas being dark.
"Indistinguishable?"
Nope. Not bio weapons. In this game you are a detective, I'm not going to spell out the answers, your suppose to explore the area and figure it out as you progress. But again can't say much here because game isn't done, story needs work, main story beats work first etc etc.
"GAME Novel?"
It's a game, not a visual novel. I've said on other sites don't think of this as a typical adult game, scenes are more spread apart then in most other games and some are hidden.
"Scenes?"
The slime scene was one of the first I had made and it's one I like the least. It was on the chopping block even, it's not that good and the thing never appears in the game again after. It came out of the sink, not the mirror but I get what your saying. The text was moved to the top of the screen rather than the bottom which makes watching it easier.
"Random Chick"
She isn't suppose to be there until you've completed the demo and the recollection room unlocks so, whoops on that.
"Tearing down and level design"
Really odd way of saying that, like you only made this to attack my game and bring my project down rather than just say you didn't have a good time with a game that isn't finished or even in alpha. I doubt you did, but it comes off that way. Levels are based around exploration as stated before, the reason the mansion is a large map is because the lower section used to have three buildings but I ended up removing them for reasons.
"Aimless wandering"
Again, other people who have played this never had this issue or made a complaint about it being an issue. Maybe you skipped through the text that gave you basic directions, I don't know.
"More save locations"
Already addressed.
"RE Inspiration"
Nope. Only the RE4 Plagas and a small section of the intro were inspirations. Never played a RE game in my life, only seen playthroughs of RE4. So I have no idea what your talking about when you say RPDs Main hall.
"Themes"
Already answered this above, game not finished, story plans etc etc.
"What does the player feel?"
No idea. Your suppose to slowly put the pieces together but the story/game isn't complete.
"Music and red tint"
The music is perfectly fine, the red tint is the sunset brother. Not sure what exactly you thought it was but it's sunset. It's an orange tint, not red by the by.
"One Moment"
Yes, because that first town was the entire game at one point and was going to be it. As I said, the iron juggernaut was going to stalk you and chase you around the area along with other enemies sprinkled in. That enemy intro was the last thing I made before deciding to A: Make the game longer. And B: Get all the main story beats in place and functional before adding, trimming and polishing.
"Too all over the place"
Games not finished, I hate beating this horse but that's why it feels empty/unfinished.
"Omni Movement"
Never liked that, it makes things very janky because of how RPGM is designed. The flashlight looks awkward and the gun gameplay wouldn't work properly. I've tried it before and I have no intentions of rebuilding my game around it when it's this far already.
"Shooting the Gun"
Shooting works fine, the flashlight issue has already been fixed by adding a better flashlight and two lantern items which illuminate an area around you.
"Nuissance Design"
I won't beat the dead horse anymore.
Originally there was two more scenes but those were cut and pushed back. I work on this game when I can and put money into it when I can. Tilesets are expensive and not worth putting money into, anyone using RPGM will tell you this.
Sorry you didn't enjoy it, if you put money into it just ask for a refund. I'm not going to ask you to stick around until it's done, if you don't like it then that's that. Just know that what you played was an unfinished project with many of your issues already being worked on or plans have been made to work on them while others aren't problems and are simply not your taste.
Didn't mean to dump text here and I apologize if I came off as antagonistic.