MTX are a necessary evil. If they're cosmetic only.
What I don't like about MTX is that I'd rather all that cool art / pets just be in the game as something very rare to find. However since they obviously need to continually make money to support the game, then sure do pets / mounts.
Still an evil sadly. Every ounce of work that goes into MTX is work that isn't going into the gameplay, new items, etc.