Hello, let me just start by saying that I do not feel offended in any way, you are free to express your own opinion as long as there is respect.
When it comes to 2D and 3D games I do realize that it's not a matter of "better" or "worse", it's about what fits the overall design of a game.
Leaden Sky is a story based horror game which greatly focuses on heavy atmosphere and features realistically designed world, characters, weapons etc. mixed with horror themed anomalies. Whatever gameplay elements appear in game they are limited by logic for the sake of more immersive experience.
On the other hand Guns, gore and cannoli is a funny, very cartoony arcade game which never takes itself seriously and has no problem sacrificing realism for the sake of gameplay. It's all about blasting heads off left and right like most classic shooters do.
Now you can see the differences those games have between them. The gameplay and general idea is completely different. While Leaden Sky has a to build immersive world, Guns, gore and cannoli does not have that requirement. Building an immersive 2D world is possible but it is much more difficult than it really should be as it requires numerous tricks and workarounds to mentain logic and realism of a flat, 2D level.
Here are exact major reasons why this game benefits change of perspective to full 3D:
1. Better gameplay:
3D gameplay gives you freedom 2D games simply don't have. In 3D everything can be your cover, you can flank enemies, lean around corners, take down targets from very far distances and do ton of other things you can't do in 2D games.
2. Better AI:
Such a major part of gameplay it deserves it's own point. AI in 2D will simply never be as good as it can be in 3D and you can really see that between really dumb AI in side scrollers and often very complex AI in FPS games. I honestly haven't seen any side scroller being praised for AI, it just doesn't work well there because of how gameplay and level design works. In 3D you can have enemies run between cover to cover with absolutely no problem, try to take out player from different angles, heights, distances, the possibilities are endless unlike 2D.
3. Better level design:
3rd dimension let's you create genuinely realistic world with tons of detail and complete freedom of movement. You can go everywhere, explore various areas, use environments for combat, stealth, avoiding danger, there is really no limit here, with more open level structure all those aspects become incredibly important.
4. Freedom of exploration:
It's pretty self-explanatory, there is no problem designing realistic and explorable 3D world, doing the same in 2D is incredibly difficult, impossible in some areas. While there are 2D games featuring exploration their worlds often have way too much verticality for a realistic game like Leaden Sky and it would ruin atmosphere.
5. Better horror and immersion:
And finally horror and immersion works so much better in first person, it's the most immersive perspective for presenting the game. Any horror elements such as monsters are running directly at your camera, it feels like it's about to jump out of a screen, this can't be compared to seeing a small, 2D player character being attacked by another flat monster, it doesn't feel personal. Additionally 3D game means 3D sound so you will be hearing positional sounds which can be used for horror, ambient and gameplay all at the same time, further improving immersion.
My final reson for perspective change is that Leaden Sky was simply not meant to be a side scroller, the only reason it was is because I didn't know how to create 3D games, but that has changed now.
The games it takes inspiration from (Stalker, Metro) are also both 3D games for good reasons.
Honestly the only good thing coming from 2D perspective is artstyle and it also can be great in 3D (work in progress):
edit: By the way, 2D game is not cancelled, it's just being developed as side project instead of main game, you can see more info in video description.
And don't worry about grammatical errors, you did good work, cheers ;)