people have realized you can't play a dedicated healer in any fun way
I can't agree with this. I have played a dedicated healer and greatly enjoyed it. But, IME, you really have to be hyper-focused on it to have a chance.
you can't keep allies up in combat no matter how hard you try
Certainly not all of them, all the time...
But you can keep some up, some of the time.
you can't add much to out-of-combat healing.
Actually, you can add quite a bit really, but probably not enough to replace (or keep up with) short-rest spending HD...
Let's see: at 7th level, a use of the Healer feat will add about 14.5 hp on average. Done twice a day for 29 hp.
For a d8 HD PC, with CON +2, average per HD spent on a short-rest is 6.5, is 52 hp the first day. But then the PC only recovers half its HD, so the next day can only recover 26 hp on average---less than the benefits of the Healer feat.
If your take the Life Domain as well, then with spells it adds up quickly--but then it is the trade-off between in-combat and out-of-combat healing.
Anyway, there is tons of healing, it is just doesn't keep up well in-combat, but was never meant to.