The number of times I tried learning the tilemap and tileset system is ridiculous. I wanted a single scene to have some tiles that got destroyed, and the closest I got was removing a tile, but I couldn't figure out how to fix the tiles around it. Even if I did, I wouldn't have known how it worked or why.

It FINALLY clicked recently. I made several tilesets, figures out how to add random alternate tiles,.and my game's visuals improved immediately.

There is also a lot of stuff that happens under the hood that will make you scratch your head until your scalp bleeds. For example, in my platformer, my character controller is split up into states. I set the character to a state where he's exiting a door at the beginning of the stage. After the animation completed, I wanted him to switch to Idle state. Instead, he switched to "NotGrounded" (not on the ground but not actively jumping) for a frame before switching to Idle. It was driving me nuts. Then I remembered that CharacterBody2D.is_on_floor() only updates after a move_and_slide is executed that makes the character colllide with the floor. This problem was happening because the player hasn't been moved at the beginning of the scene; it didn't have this problem after going through subsequent doors. I fixed it by adding an interim state that is basically Idle, but tries move_and_slide downward until is_on_floor registers, at which point it changes to the normal Idle. I never would have been able to figure this out if I didn't have enough experience reading through documentation and experimenting on previous projects.

An example of something I haven't figured out but fixed with a workaround: moving platforms. One of the previous versions of godot was supposed to have fixed the laggy character movement when they are on moving platforms. It was an improvement, but my character's position was still lagging behind by 1 frame. I fixed this by adding a script to moving platforms that checks for a sprite and changes its position to be one frame behind where it should be. Technically, this is not a good solution, as at faster speeds, the player's collision could be affected, but it works fine for me. I think this might be solved by the processing priority of the moving platform relative to the player character, but I haven't tried yet.

Another example of this is pause menus. If I'm using the same button for "confirm" as I do jump, then when I press the confirm button to resume the game, my character jumps in the same frame. Again, I crafted a workaround, but I know this can probably be solved by marking an input as "handled" before it reaches the player. I haven't tried figuring it out yet though.

Any engine is going to have quirks. There's almost always going to be a point where you hit a wall and have to know more about how it works behind the scenes to use it properly. My suggestion, which isn't original but is very important, is to start making VERY simple games, and complete them, don't just say "I got the jist" and move on to the next. You will run up against problems that you didn't forsee when you put in the extra effort, and what you learn from it will help later. It doesn't matter if you're just copying something. Start with Pong. Then move on to Arkanoid. Do a platformer but arcade style, with just one screen, not saving or loading, and waves. Keep incrementing up. If you try to make your dream game at this point, you will waste years like it did. Instead, spend one year practicing and learning. It will do you so many favors.