Sorry but this is a Dunning-Kruger type of post. It's good that you're making progress on your game and increasing your knowledge but you're falling in the trap of thinking that you can guess what the entire picture looks like just because you've seen a glimpse of its corner. Some things are relatively simple to code by themselves but inserting them in a giant machine full of many different parts made by many different people and then ensuring that everything plays well with each other... well that's never easy. That's the kind of thing you don't learn to overcome by reading theory but can only be acquired through experience. I'm referring to software here since that's the focus of your post but the other point is that art/music/design is magnitude harder to learn and can also only be acquired by grinding a lot. You always have to "just put the time in" but it's called difficult because the vast majority of people attempting it fail.

At the end of the day, it's easy to tape up a simple game, alone, with store assets and a pre-made engine but making a good high quality game that can compete with what's out there on budget/time is difficult... If it wasn't, everyone would do it.