Oh I can definitely help with that! I know you use Godot, but here's all the things I do to get that effect:
1) Pick a color palette and use Aseprite to adhere all your art to it. You can do this with existing art by setting the color mode to Indexed and then changing the palette to your custom one.
2) There's a Unity plugin I use called DoTween Pro that is incredible for making your game feel polished. Essentially any sort of movement you'd have in your game such as the player moving or a button scaling up when you hover over it, gets tweened to have a bit of an elastic effect. Try to find ways to have things animate that you normally didn't think of.
3) Have slick interface sound effects for most interactions in your game. This combined with tweening makes your UI look really responsive and crunchy.
4) Put juice into damage effects. In this game, I use screenshake, particle effects, sound effects, a scaling tween, and I flash the enemy white for a second when they take damage.
5) This might not apply to you since it's a Unity plugin, but for the lighting, I used this plugin I found on reddit: https://www.reddit.com/r/Unity2D/comments/12bju7i/stylized_pixel_art_lighting/