And perhaps if they added the missing classes and races and some armor and customization options, and new companions, it would be more interesting to replay from a gameplay point of view. You can't keep replaying just for the same story.
I think this is the crux of the issue. There's nothing to playtest or give feedback on that hasn't been done so far. In one year Larian has added one class and not much else for EA players. I personally haven't touched it since the first patch or two since I can't be bothered to replay it again without any new content.
For myself and likely many others to even bother reloading the game, there needs to be some new companions and classes if nothing else. Of course more content to act 1 wouldn't be looked down upon if they decided to expand the area a little or add more quests.
I'm largely concerned with the fact that Larian appears to function within a bubble. Even in terms of act 1 with analytics and at some point a million different players, communication is incredibly poor, updates are scarce and interpretation of the data provided appears to be biased. Now imagine the final release when we've been unable to provide feedback on any of the other companions, classes or content the game has to offer. The rest of the content will be entirely produced within the vacuum that has become Larian's development team. I just hope that Baldur's Gate 3 Definitive Edition is a free upgrade.
Edit: To drive the point of the OP with the Steam charts. Less than 1 in 24 are still playing which means roughly 96% of players stopped playing compared to the initial release.