Okay I am playing only WHM and that is my perspective:
As a healer without shielding (and back then no instant heals) it was very fun to learn to pre-cast your heals and time them perfectly so that they land directly after a tank buster or a raidwide, so that the HP bars basically jumped down and back up in a fraction of a second.
Sadly that is pretty much gone. Tanks solve tank busters on their own now. You can throw them a Divine Benision however. Not as much fun but it is something. And even if the tank takes damage you have more than enough instant heals available that you no longer need to pre-cast a heal.
But you can still pre-cast a heal for raid busters. And I do. A well timed Medica 2 + Assize or Afflatus Rapture right after will instantly heal everyone back up. And the HoT from Medica 2 will fill the last percent of the HP bar.
But of course using Medica 2 is a dps loss. And holding Assize to use it for healing as well.
I liked ressource management. Balancing Cure and Cure 2, fishing for Freecure proccs and keeping Regen running on the tank was fun.
That's basically all gone now. You only use your strongest heals all the time now. Tanks most often don't need a Regen anymore, but I still like to use it from time to time - even if it is a dps loss to use it.
I like to find ways to make the most out of my Lilybell.
Timing it perfectly so it can cover more than one raidwide or placing it in the middle of the arena when we all have to spread for splash AoEs and I can't cover all people with my heals by myself due to range issues.
Or using it as a form of mini LB when everyone messed up and the next raidwide is coming. That 1000 potency AoE heal is handy to recover the impossible.
And of course what I like about all casters: Optimizing movement and "positionals" for mechanics and - as a healer - also for AoE heals.
I like to optimize my healing - not my dps.
Using the right heal at the right time.
And yes I like to use my GCDs, even if that means I will only cast 148 Glares at the end and not 152.
Plus the big canes have style.
Queue times are nice as well. Playing the game is more fun than standing around waiting.
And I like my WHM exclusive headband.