What the hell is "linear" supposed to mean anyway? MoP is probably the most non-linear leveling content in WoW. You can literally go wherever you want as long as you meet the level requirements. Neary all quest hubs are independent from each other, which is radically different from Cata, where every damn thing was scripted back and forth.
Seriously, what do you want? Pre-made lv90ies? All you have to do is do a few quests here and there. Eventually, you'll be there. If you don't feel like it at all, then don't do it, but I think you should simply accept that if you aren't willing to put some time into it, you can't have another max lv character, just as you can't have a full epic geared toon if you never raid. Where's the problem.
In fact, it's actually a good thing that it does take a little while, as it only prevents you from running the same endgame content simultaneously on several toons. It keeps things fresh and keeps characters on differerent stages of the game. That would be the next thing you'd be whining about: how the dungeons and raids are sooo boring and how the endgame content is sooo repetitive and how there's not enough different stuff to gear up with.
That's a major problem with the short attention span and lack of patience with people today. They're simply not able to keep something for later and must have everything NOW. It really breeds borderline bipolar behaviour between manic and hyperactive and bored and burnt out.
Must you take things to extremes?
No, in Northrend you could just as well start at another place, nothing was scripted.
I didn't even touch Borean and I could enter and quest in Dragonblight just as well.
No, I don't want instant 90,s, this was never the case, you just overdramatize it.
Yes, several toons which all have different abilities, looks and themes IS fun.
The day I realized I started feeling sick to my stomach whenever the LFG thing popped up, knowing that it'd be the monastery or the palace again, was the day I realized I don't need more lvl 90's! Whose bright idea was it to have only 4 levelling dungeons for the last 5 levels? 80-85 at least had 7.