I'm genuinely confused. Isn't the "control single character and have party follow" method how every 3d crpg has done things? That's how it was in NWN, NWN2, and Dragon Age Origins.
I can't quite remember NWN2 control scheme,. But NWN and DA:O weren't really party games - NWN you controlled a single character and in DA it was the same - and I am pretty sure there was a more classical control style when going into tactical view. Either way, none of those games required anything more sophisticated - exploration was very basic and environment irrelevant.
D:OSs (and BG3 from what I have seen) isn't like that - and it requires a fine micromanagement of your party members. Default Larian system simply isn't sufficient for it. Its not that it doesn't allow for fine control, but it far more clumsy when played that way - and I found it far easier to commit errors (classics being stealthing someone and forgetting to decouple him from companions so they rush to him once unstealthed or leaving someone behind).
Ahh I am pretty sure there was a 4 party system in DA:O. I know that I would control all members of the party to get combos to work in difficult combats, Sure against none boss fights just let the AI control the rest of the party but in boss fights on higher difficulties I was ALWAYS taking control of the entire party in tactical mode. maybe that was just me.
That said i think other games have handled party movement better than BG3. I think the system works great in combat but is clunky when transitioning into combat and clunky out of combat. i have been able to fine tune my party's tactical positions during combat with relative ease with the combat movement mechanics but outside of combat the OP is spot on. And as has been mentioned above the transition into combat is terrible.