asking why tanks gameplay and enjoyment is important is ridiculous, No one is saying that it isn't important for healers to feel valid in the party and that they should have more to do (frankly anyone who is against healers having more to do, just doesn't obviously play healers), but you act as if stuff like holy sheltron regen would actually fix your issues with healer design, they will barely make a difference, I mean did you heal old endwalker dark knights much? I know I didn't need to especially during boss fights that's because they have tons of mitigation and very little damage.
I feel like your the one throwing your hands up, by insinuating that we should just accept low damage output and nerf tanks so healers can have the fun while tanking becomes even more miserable for people like me who enjoy supportive cooldowns, because funnily enough I don't just play "paladin" to be a Mitigation and aggro bot, I play it to support and help my team partly as well. (which includes a bit of healing... surpise I want to help contribute a bit of healing as a "paladin" funny that...)
Sure changing damage profiles and only nerfing down some sustain aspects wouldn't fully fix healers or tanks in older content, but I don't really see why we should let the old content hold us back, it's not like old content is actually giving any attention or care for balance.
All I'm saying is that tanks and healers are both important, you act like we have to sacrifice these things (even skills like curing waltz that can add a little but of positioning nuance to dancer), for the sake of healers being balanced and all I've ever said is no we don't actually need to change too much outside of obvious over bloated self healing such as pld healing off the blade combos or warriors entire kit at this point.
Tanks could also take some healing pressure off healers, I think a difference a good tank should make is the fact they may save healer some gcd heals to help damage with good communication and teamwork, the issue is you never need to GCD heal because the entire lack of damage issue, with frankly both healers and tanks having way too many mit/heal skills, so theirs no actual skill expression of using these said cooldowns currently on tanks, but I want that i want to work together with healers as a tank in this team based game.
All I'm saying is that we can have our cake and eat it too in this situation, maybe we might have to make some changes and I fully agree on nerfing sustain, but I draw the line when your so insistent that every "free" healing cooldown on a non healer must go or you will not compromise or be happy.