Thanks for taking the time to actually try and relate or understand some of the issues that players have...
As much as I criticize everything, you would probably enjoy the game even after Shadowbringers, and well into Endwalker and Dawntrail, purely because you're in a state when you still have a lot to consume between expansions.. Realistically a lot of people that are complaining have been long-standing players... So they have consumed a lot of the content all across the board, and they will have been coming from a time and place where the game (in their view and mine) was much better. Not only that, having so much to do, means that you're able to do the story at your own pace (many people have only been able to do nothing but story, just by virtue on how long they've been playing and how much they've done)
As for why the community feels that way.. See the above...
For a little more of a detailed answer, for many players they had been playing when the game demanded a lot out of you, so it was capable of keeping you occupied for very extensive periods of time, and this was even without needing to diversify your content consumption. For instance in the days of HW/SB, you could comfortably just do crafting, and nothing but crafting (and it would keep you entertained and occupied outside of the number dopamine that consumes modern crafting). The game generally speaking would demand your attention a lot more, and for people looking for that, it was an amazing game, I am one such example.
The game since then has streamlined more, so activities like crafting no longer really demand what it used to, but is now a much more approachable content type.. Obviously this is something else where it's very much preferential.. Do you want something that you feel like you can drown in? Do you want something that you can maybe play a couple hours here and there on a weekday.
I sometimes say to myself that had I never started as long ago as what I did then many of my complaints would not be as stern as they are, just because it's by courtesy of having something to compare by, or having a reference point from how the game was.. At least as a newer player, then the only thing you really know is the current state. I know had I not been playing as long as I have (and since when I did), then my enjoyment of the state of the game probably would be a fair bit higher.
It's always difficult with this, because you're trying to get people to relate to you without ever having experienced it themselves.
Then you have the issue that the last exploratory content was over 4 years ago this is obviously something that has only happened once, and exacerbated by the absence of this content from Endwalker.
I think it's a decision you need to make for yourself, as a lot of the issues that people have and that people see (even if you may agree in principle) you may never encounter, just virtue of being a newer player.