Game art style was unique, music was good and content was there but controls are just terrible.
There are a lot of examples about coyote time, jump gravity etc. and you should definitely check it. What is worse about this kind of problem is you have to do it at start. Even if you change how the character jumps now than you would also have to change the levels which is a lot of overhead.
A very good advice I learned is that your main character movement should feel good even in an empty room. This is also a very good way to start a platformer.