Overall, I agree. At least in the sense of what the "ideal" would be in a game. I love the origin characters and their stories (for the most part, anyway). That said, I was surprised that there was not an option to make them level "on their own" and that I was instead in full control of how they progressed from a leveling-up standpoint. It made them feel more like characters I was molding into what I thought they should be instead of what their stories thought they should be. I always sat there trying to think about what they would decide for a skill, spell, or feat. Ultimately, however, because the choice was mine their character development felt more arbitrary. On the other hand, I love to spend a lot of time in the level up screens considering all options - so that was fun.
I would also agree that their truly independent personalities and natures where really strong in Act 1 and then seemed to taper off after that. The companion quests did help keep some of those moments intact, though, throughout later acts. Your comments about them not doing anything while at camp are valid.
Ultimately, your desire to see this kind of depth in character development would probably mean that they would not be received well as playable characters. A trade off, to be sure. One I can see both sides of. Overall, though, I will say that BG3 has done an exceptional job of providing intricate character options while still offering the ability to play and shape them to your liking.
