I disagree that hub-and-spoke is no longer necessary from Austin. While AUS is extraordinarily well connected to the largest business cities, lots of business can and does take place outside of that, and even among those cities, there still is sub-optimal connectivity in terms of schedule. Take Ontario, CA as an example. It's in the 13th largest MSA. And if you happen to be flying on the 4 days a week Frontier offers service, and happen to be traveling on a schedule that fits its single flight on those days, then perhaps it could be a viable option. Beyond that, you're going to have to connect. And in order to do that, you're going to be using some iteration of a hub-and-spoke system.
You're absolutely begging the question by saying AA fails at "everything." Without quantification, it's just a claim with no substantiation (and a pretty lousy one that's riddled with emotion at that). Good luck getting to a city like Chicago on JetBlue. Maybe if you leave by sunrise you'd get there before dinnertime.
There is almost nowhere in the continental United States you can't get to in 7 hours or less travel time on AA, UA, or DL from AUS, including secondary and tertiary cities. Of the three, DL would far and away have the worst schedules because its hubs are the farthest. No other airline can offer that kind of connectivity, and it's thanks to, yep, you guessed it, the hub-and-spoke model.
Pick a major destination from Austin. AA will get you there just as easily, if not more easily, than every other airline out there. They fly nonstop to 6 of the 10 largest MSAs, compared to United's 5 and Delta's 4. Of the three legacy carriers, AA and DL are tied for the most nonstop destinations overall out of AUS with 8, and AA has the most passengers carried. So your claims that their itineraries are the worst just really doesn't stand up to any scrutiny because they go the most places and carry the most people which means they have the most flights (all carriers are almost completely mainline with comparable capacity, so one isn't being boosted by more frequency using smaller jets).
They also have the newest fleet of the three legacies, and while I fundamentally disagree with their floundering strategy as it pertains to cabin service and in-flight entertainment (DL wins easily in these categories), you're far more likely to be flying on a newer plane.
Last year, AA's on-time average was indeed the worst of the three at about 78%, worse than United's (79%) and Delta's (nearly 86%). There's certainly not a lot between AA and UA and the average customer doesn't fly enough for that difference to be significant.
Customer service I'll concede is a black mark on AA right now, though I've had pleasant experiences by and large on all three and wouldn't generally put one over the other.
The whole point is that people travel for lots of different reasons, and even for people that travel regularly, AA provides as much utility, if not more, than any other airline that flies to AUS. People value things like robust schedules with lots of flight options (which knocks out any airline except AA, UA, DL, and WN), lounges to escape the busy-ness of the concourse (which knocks out WN), frequent flyer programs that provide status, upgrades, and mileage accrual (could further knock out WN depending on what you're looking for).
Of the three, I can get more flights to more destinations out of DFW with AA than I can at IAH with UA. DL is a nonstarter due to too many areas where I have to backtrack. There's an enormous arc in the center of the country from SLC-MSP-ATL where I have to backtrack if I want to get there. This goes to your point about the DL focus city which I think we all hope is coming. Combine that with the fact I hate IAH as a connecting airport (and I say that as someone who will be based there starting in 2 weeks) and AA almost wins by default.