I don't disagree with you, but considering there was never a promise to fix anything at all I see our current situation as being pretty fortunate. The team communicated from the get-go that Hrothgar and Viera would be a limited race: one gender selection each and unique hairstyles. They would never just take hat mods made by creators and implement them into the game even if said creators were offering to give away or sell their work. They've been adding tons of QoL features for combat/raiding that have already existed as plugins for ages, but they didn't ask the creators of the plugins for access even if it would have meant an easier job for them. They just redid all of it themselves and in their preferred way.
As of yet there has been no promise that we will get any sort of extra hat compatibility. That doesn't mean the announcement won't eventually come, but it isn't a "why don't we have this feature yet?" thing for me. There can't be an expectation of something that hasn't even been officially addressed since Shadowbringers.
I think we have a few potential scenarios from here on out.
Best case: we get an announcement between now and 7.0 that they have been slowly working on headgear and it will all be ready alongside female Hrothgar when the new expansion drops.
Worst case: 7.0 brings only female Hrothgar in a state as up to date as male Hrothgar and we continue being drip fed hairstyles every patch.
In between case: somewhere in the middle there's a third possibility where they release hat compatibility the way they've been releasing hairstyles: in batches.
Even in the best case scenario we're waiting until the next expansion, and that's a massive "IF" to begin with because, again, nobody has addressed this subject in a long time. I'm definitely hoping as well, but there's no way they don't know how fervent the requests have been. After male Viera/fem Hroth I really would be surprised if hat updates never come. I know it sucks to always have to think "patience" but that's the only realistic approach. I can't be disappointed about something that was never promised to begin.