Mixing vocals properly is one of the foundations of producing music. Our ears are evolved to hear human speech clearly, and therefore working with vocals means working mostly with the frequencies to which our ears are most sensitive. Therefore the effects applied to vocals are the easiest to hear versus other instruments, and vocals are a place where it’s probably easiest to overdo effects.
At the same time, everything learned about effects and ways to make vocals sound good can be applied to other instruments. The equalization and compression techniques shown in this Ableton tutorial are things that can be used on virtually every other part of your track.
Finally, crap in = crap out. Getting a recording from a really talented vocalist will make your tracks shine, while getting parts from not very skilled vocalists will sound bad or require huge amounts of auto-tune to get a very fake sounding vocal. Work with the best and good luck!