How good do you guys think "star artist producers" (couldn't come up with a better "name", sorry) would sound without help mastering and mixing? Would it have a huge impact on e.g. David Guettas or Skrillex (sorry for picking Skrillex guys but I love him and his sound

) sound? I'm fairly interested how much credit they should receive for the sound they create. I do not question their skill at all, just interested in how much 3rd part is involved.
I'd also love to hear someone here who is a professional producer (not DJ) making glitchstep or anything fairly melodical before any 3rd part is involved. Like a sample or w/e.
Cheers everyone! Och glad midsommar! And sorry for any stupidness, I'm new to producing.
