Thanks a lot !
Yes, Selkione told me the same thing. It's partially due to the reverb that stays too strong on the final and the instruments that are probably too much on the same octave. But yes, the mix is muddy and I probably used too much loops that were not designed and thought together.
That's not a real excuse but I tried for this project to compose on my own software and it allowed me to see the main issues for composition. Like a timeline that lacks clarity and usability (I was not able to position the time cursor, I could only listen to the entire song which made the final mixing tricky).