We could nitpick about what is really an open world game and what is not, but BG3 is definitely not AT ALL like BG1 and 2, Dragon age Origin or Mass Effect either.
Probably the closest comparison I can think of is NWN1 campaign - just erase transitions between different bits of the map. Outside D:OSs of course, that used the same structure (and narratively suffered from many of the same issues. Once again the map consists of multiple, separate zones with little thought put how characters in zone A would react to proximity of zone B. Shockingly, BG3 is not even that bad, compared to what we had in D:OS2.
