To be fair, a lot of the systems in HW were equally only improved and innovated on in later and subsequent expansions. It wasn't until Eureka Pyros until they actually managed to sufficiently iterate on large scale content, which was over more than an expansion later, for example. Over 2/3 of the expansion itself was a borderline trash experience for many players. No amount of late fixing still changes the overall perception of how bad many people found HW, now how bad it was for the game.
Scrip system? Wasn't even properly reflected on until Stormblood. A lot of people were raising many complaints with the red scrip system, even early on in the game. Yet, they did nothing for a very long time, and instead let this abysmal system fester for an entire expansion.
Specialist? - They still elected to try and ram an awful and mistakenly specialist system down your throat for an entire 2 expansions before they realized people still didn't like it. They knew people didn't like it, but they absolutely weren't bothering to look at why people didn't like it otherwise it would not have taken them so long to come up with the solution they did
Favors? - They determined that the best course of action was outright removing them from the game, essentially. - Same thing with Matron and Patron Diadem. If you think V&C was bad then you ought to experience the OG Diadems. Once again also so poor that they had to remove several times, before eventually permanently removing it and repurposing for Ishgard Restoration. The EM was a chance, within a chance, within another chance at getting a weapon. There was the chance you get it in the first place, on top of the chance it was actually for your class, and then a chance that it actually had favorable substats
Yes, they did listen and eventually fixed it, some systems in that same expansion had the courtesy of getting fixed in given course, however, many, many of them weren't even addressed in that expansion, and only got addressed in the subsequent ones. Some feedback they listened to, some they absolutely didn't. and much of the feedback was unironically deleting actual streams of content. It's all well and good saying "Well, they listened here, and they listened there, and some of it was improved in Stormblood" - But it doesn't change that of how was when sticking true to the Heavensward experience.
Some of the systems in Endwalker will be seeing this same treatment, e.g., "Lifestyle content" - Pretty sure they have already reflected on this to understand that they didn't nail a communal aspect to any degree. IMO, no amount of "Fixing" would ever make Island Sanctuary into something palpable. The very best they could do with that is enabling one player to help progress another player progress their island, e.g., gathering or tending to workshops.
I will just say that I think both EW, and HW are mutually the worst expansions, each for their own reasons. Yes, they took lessons in HW. However, no amount of lesson-ing is going to change the simple fact that it was a drab experience for the majority of it. Just equally as EW is a drab experience because it doesn't give you a reason to actively participate in the content. As I've said elsewhere, you can certainly like them for personal reasons, but that doesn't necessarily mean that either of them are actually good for the game relative to the community.