What I'd like to see is an airline with: * Single-class seating * No frequent flyer programme.
First and business class create weird perverse incentives: they'd rather leave seats empty most of the time in the hope they'll get a few business travelers not spending their own money, or people who managed to grind their way to Triple Oganesson status and managed to drag an upgrade out of the system. The rest of the time, it's just an obnoxious reminder that they could be providing a better experience, but you're not paying them enough to get it.
Frequent flyer programmes will never make sense for a large section of passengers. So again, it's just another thing to hassle customers with, either as extra steps in checkout, or a place to say "well, if you spent enough money with us every year, we'd let you skip to the front of a queue."
I think the most flights I've taken in a year was four return trips, to two different destinations, using three different airlines. There's no way I could generate enough points to earn meaningful status or "free" travel in a practical timeframe, and even if I could, it's not going to change the fact that many city pairs have limited service choices. I'm not sure there are enough points you can give me to justify injecting a 50% price premium, flight change and four hour layover into a trip that's three and a half hours if I go direct via $other_airline.
The best I could do is instead intentionally select a rewards credit card programme, and attempt to divert spending to that to attempt to rack up points. If I'm going to use a rewards card, I'll use one that reimburses me in actual money, instead of a corporate scrip subject to surprise devaluation or blackouts. Theoretically if I line everything up just right, I could get 42% back in the form of Air Koryo Fun Points, but only if I use the card on months with no "R" to buy UberEats delivery of pork rinds. By comparison, 1.5-2% of hassle-free American Dollars across any purchases feels like less of a cryptic puzzle made by a DM who spends too much time in Excel, and more of an actual incentive.
Give me 6 inches extra width and legroom. That would be 30% wider, and about 20% longer, for a total of 156% of original total area. It would make everything feel so much nicer that I'd gladly pay 156% of the ticket price, if not more.
Instead, many routes are either cram in tight for cheap, or buy a first/business class with room to lay. Just give me something in the middle, please...