Fine tuning is a huge deal. I made some simple games and spent a lot of time on fine tuning little details about the movement trying to nail the right "feeling". The feeling of Mario's movement in Mario 64 is excellent. That feeling immediately makes the game fun even when just jumping around aimlessly.

It's very difficult to get right. Even with the exact same programming logic, tiny tweaks to certain numbers around velocity, acceleration, friction, impulse, etc all can have a huge impact on feel. So even without changing anything besides a single static value here or there you can make the game feel very different. (and then of course you can also add more logic and tweak things endlessly, like adding coyote time, jumping higher when you hold the button, nudging the player slightly into place instead of stopping flat if they are grazing an object... and then other things like sounds and animations can themselves completely change the feel without changing the systems at all)

Feel is also something that is very subjective. Some people might like something that feels very tight and responsive, some people might like something that feels more floaty or forgiving. I tweaked one simple game I made to be a bit quicker and tighter, which caused more casual players to feel it was too hard and quickly stop playing, but more competitive players got highly engaged and played over and over to climb the leaderboard.