I' glad my word have reached you
It's something that I've been concerned about for a while, trying to find ways of fixing it without remaking everything, but you've got a very objective view of the problems and it makes clear that patching up the map would not be enough.
It takes a while to understand what's good design in your own game (since we are not copying a game mechanic per mechanic). Me personally had to remake the tutorial from ground up 3 times, and the first levels. Also consider the Romero tip: "the first level should be the last one to be made". In our case we can't really do that, we need to explain to testers how the game works, but redesigning a level from zero imo it's not a shame, because we need to craft a smooth experience for the player.
the game itself is meant to be niche. It's going to be a difficult game (not the same way it is now) with weird design choices and humor.
There is no problem with this, imo the only unexcusable thing is an unfair challenge, aka gathca moments. Take a look at Floe playing "i wanna be the guy", then see some games you like that are known to be hard but fair (super meatboy, 1001 spikes etc). Extrapolate lessons on what to do, and what to avoid; also test gameplay lenght checkpoint to checkpoint. Consider that you are devvin a metroidvania, so the road from A to B will be different from B back to A. In some sense i could also suggest you to try to dev pieces of the map as a stand alone levels that connects and fork at junctures; or go classic zelda 1, with an overworld and dungeons. you can do anything.
I can't tell what is wrong, maybe it's the color choice or the shape of the entrance, I don't have much idea.
In my case it was the shape of the entrance. Also gfx design it's a continue work in progress, so gl with that
Btw, swinging your sword from low to high feels very strange