I once saw a post: “how to make a better platformer” or something like that, but I am no longer able to find it, so i have no visual example.
What I think is rather easy and would help a lot: If the player presses the jump button right before the character lands (2-4 Frames), perform a jump as soon as the character lands. (Instead of ignoring the jump-button and letting the character run straight into the lave :) )