To be fair, Theorycrafting can be fun in itself and some people do not really want to put the theory into practice... but if they want to, they are kinda putting the cart before the horse. Spending so much time planning something that you haven't even tried yet is risky... you might waste a lot of time planning something that doesn't work in practice.

Yup, that's very true. Fits quite accurately with my situation!

Thank you very much for all these answers, I'll definitely try to change around my working scheme when it comes to developing games.

is it normal for a game developer to get burnt out of their own games?

All the time

is there any tips for telling if a game is going to be fun from the start? I know I'ts a very subjective topic, but i guess there should be something that separates fun from boring?

Let us play it and we'll with the most sincern honesty in our hearts tell you what we feel. (I will anyways, Don't know about everyone else. They might be too nice.....)

in a marked so overcrowded like the mobile games' market, how can one boost their creativity in order to create something fun without feeling like somewhat of a copy of other games?

Ask god. Not being mean this is only my best anwser so far.....