Me too. Actually walked away from some 'alpha upgrades' because the were not imo player friendly. And I don't suspect A21 is gonna be any more friendly. Livable? Sure, but even using that term indicates TFP messed up on our interpretation of player enjoyment, agreed? And as 'for the better', we'll have to see. Better for whom? But, its all moot. They gonna do what they gonna do, that's been proven. Now, if they'll just release the damned thing....
Player enjoyment is a complex thing. To make an easy example: Players like weapons with huge damage. A naive improvement to a game would therefore be to increase the damage of all weapons. But the result would be that most players don't feel challenged and do NOT enjoy the game. The game has to be judged as a whole, not each feature in isolation, and that is what many players fail to do when they go from alpha to alpha.
Secondly players have different tastes. TFP has changed the feel of the game while they were adding and experimenting and with that they also changed the target group of players that would welcome all the changes they made. Just as an example, before they could add RPG advancement features they had to present a playable game, so the game was a lot more sandboxy and had no RPG advancement. That appealed to different players than the current game and the more RPG they added the less some old players liked the changes. But that doesn't mean that they failed with RPG advancement, it meant that their final target group of players is not exactly the same as the ones drawn to the game initially.
You correctly say that "our interpretation of player enjoyment" was messed up if you just look at yourself and players having the same taste as you. But you overstate the case if you generally say alpha upgrades were not player friendly unless you specify exactly which group of players you talk about in regards to which change.