I'm 5'11" and there is plenty of room in Economy plus. If you're a frequent flyer you can get Economy Plus for free when you book a ticket on United, I assume Delta is the same for their frequent flyers.
Over the last 5 years United Airlines has had an average profit of 0.2% Delta : 7.3%. Southwest: 3.2% American: -5.3% (loss). JetBlue 2.9%. Those are very low profit margins. I'm one of the first people to call for government intervention when warranted but the airlines don't need to be bailed out or subsidized just because people aren't willing to pay the cost of an airline's seat. If people want lots of leg room or they're slightly taller they can pay for the extra space they want. If they want a super cheap, basement discount seat in exchange for a little less comfort then I don't see a problem with that either. Should we outlaw small cars too because they don't have large trunks?
Either one of two statements is true:
1) Access to air travel is essential to people of all economic means.
2) Air travel is a luxury.
If #1 is true then we shouldn't be forcing airlines to increase their prices. We shouldn't force airlines to increase their seat spacing since it would price many people out an already expensive product.
If #2 is true then we shouldn't do force airlines to increase their seat spacing because it's simply a luxury good and if people want a slightly nicer luxury they can pay for additional expense if it's truly valuable to them. And if someone really wants to know exactly what kind of seat they're in for when booking... they can enter it into SeatGuru and check.