

Ok, but you understand that even at a reasonably low level “plugins” exist for core functionality.
Libraries within code exist to make certain tasks standardised and easy to implement. Game engines abstract common requirements like level loading, control schemes, camera movement…
The point I’m repeatedly making is that these things already exist, and if a designer chooses to implement them one way or another, then I suspect they have a reason to.
No one sets out to make a half-assed game. Even the jank out there was probably a better idea at one point. But often that comes from hubris, not from a lack of “plugins”.
Again, I used to do this as a job. I was pretty mediocre, but I did get to work with some amazing talent… And I think they’d back me up on this. Creating cm games isn’t about standardisation, it is often about exploration. It is an art form as much as it is a technical process.
However, I highly recommend you give it a go yourself. GODOT is a great engine with a ton of functionality and plug ins as well as tutorials. Spend a week making a very simple game with very simple controls. Do the thing and report back. I promise I’ll play it and I’ll celebrate it with you.

It’s your assertion that “Devs don’t implement these sort of things because they would rather spend their time on things that make their game different” that I disagree with.
That’s just not how it is. Serious thoughts goes into the mundane stuff. The UI, especially.