Introducing job boosts doesn't day anything past that the devs thought that was a good idea. It might be true that most players don't enjoy levelling, but I haven't (so far) seen any evidence of that.
I could see an argument that introducing new jobs at a higher level indicates that the devs wished for us to not have to do earlier levels, so I'll give you that, I have no counter.
I agree, your jobs feel incomplete at lower levels because they are incomplete. That doesn't mean there's anything wrong with that. Say you go into sastasha as summoner, sure you can't summon bahamut, but you can still play well. Yes, you'll know what you're missing, and what skills you would like to use, but that's not an argument that it shouldn't be played at that level or that there's not enough kit.
It's up to individuals how they get those levels, none of my business if they level it or job-skip. I disagree that it takes a lot of time to level, because it's not that long, especially when compared with the time other things in the game take.
Rukia, no player is forced to pay anything beyond their subscription.
If a job starts at level 1, you are not forced to buy a skip potion. Levelling remains a one time thing, it's not the end of the world if it takes a little work.
What's wrong with putting a little bit of time into a job you want to play? I doubt there would be so many people upset as you imply, merely a vocal subset who want to take it into raids or msq or their content of choice.