...I understand, to a point, the why.
In vacuum, it means there's nothing to really optimize. Situation X pops up and you hit somewhat whatever your hand activates first when you just smack your controller/keyboard without looking, and it solves the problem.
But I think this is a thing we agree on - such changes shouldn't be done in a vacuum/stand-alone/aren't the only things that should change.
For a very simple example, imagine a world where all your GCD heals aside from Cure 1 cost a lot of MP and MP actually was relevant. It isn't right now, but this would be a change. Now the "random smack your keyboard" style of "gameplay" goes away. Chain casting Cure 3 makes you go oom and now you can't do anything. Being DPS neutral doesn't change that if you have no MP to take any actions at all. So there would still be consideration for what the best tool for the moment is. If Cure 3 and Medica 2 cost 2000 MP, for example, now there WOULD be cases where you might consider Medica 1. Right now, there's no time you'd ever use Medica 1 over Medica 2 since it has a shorter range and Medica 2 does as much healing even as chaincasting Medica 1 (more or less) since the first HoT tick makes them equal, and Medica 2 has a 5y longer range for a miniscule 100 more MP cost which is irrelevant if you're using Lucid on CD anyway. Further, you'd still have to consider things like overcapping Misery, which you might sometimes still need to do if you were having to cast more GCD heals with more healing intensive encounters. And there are times that things like Tetra would still be useful options, such as when you have two very damaged people before a pre-body check AOE (that is, where the boss AOEs and would kill them, causing the subsequent body check to fail) where you might Cure 2 one and weave Tetra oGCD to heal the other before the attack lands, thus salvaging the attack and body check.
It takes very little thought to see how just making GCD heals damage neutral wouldn't make the entire world end, but rather would add more interesting choices and optimizations - because "oGCD healing plan + Glarespam" clearly isn't more interesting. Hell, if we just made GCD heals damage neutral RIGHT NOW and DIDN'T change anything else, that would STILL be more interesting. I'd have the option to roll HoTs across the party or not, which is already more interesting than Glarespam.