A lot of these games are working off of an assumed learned collective memory.

Think of movies, and their tropes. How do you understand that when a movie cuts to black for a second, and then suddenly shows a new location, that we did not just teleport? That the black cut indicates the end of a scene, and the start of a new one?

Think of how many games assume you know which button pauses, which opens the menu, which buttons move the character and which ones make you jump. Now, add another layer of controls. And another.

BG3 is also working with an assumed collective memory from DnD. Assuming you already learned about class vs race, and cantrips vs lvl spells, and turn order, etc.

It sucks when you miss large games that establish these things, but its also how art forms evolve. Games just dont yet have a way to easily re-teach them.

For BG3, don't search something about it, just start and play. You don't need to know anything prior, however it's a role-playing game so play accordingly what kind of character you created. You can save-scumming if you want if some desicion you made leads to something bad, though they all the part of the game. Just play and experience.

For games like Overwatch, it isn't complicated at all. It just requires you to play it constantly and learn counter measures just by playing. Learning them is the fun part, overthinking about them not so much.

To be fair when I see "complex game" part, I was kinda expexting some advanced building games, something like Factorio, maybe RimWorld.

Anyway, also you don't have to like any games even if they are overwhelmingly positive titles. Just find what you like and dig in.