It's the people themselves. We've all had those motivated teams of FAs who work together, pay attention to their passengers, and do the little things (checking for drinks, etc.). They make a noticeable difference.
Instead, too many people -- in all aspects of life, not just AA -- do "what they have to" and nothing more.
Let's face it -- how many of us are "on our A game" 100% of the time? My clients can't see me rolling my eyes over the phone every now and then, and they certainly can't here what I say when on mute -- lucky for me! FAs and GAs don't have that luxury...we see every step of their "at work" performance. I'm not excusing it, but I understand it.
If I could, I'd mandate that: (a) every passenger said "hello, how are you doing?" the first time they encountered each line employee (ticket desk, security, gate, FA), (b) every TSA announcement began with "ladies and gentlemen", rather than a bark, (c) every gate agent provided a status update (re clearing upgrades & standbys and the ontime situation) via PA at the gate every 5 minutes starting 15 mins before scheduled boarding, and (d) no FA spent more than 15 consecutive minutes in the galley (except when on break).