It sure doesn't play like older BG games, but there is a big similarity. They are both the pinnacle of what CRPG are in their respective period.
But having that in common doesn't mean BG3 feels like a sequel, even if BG3 is labeled as the best crpg of the last 20 years that doesn't automatically makes the game a ''good sequel'' you know what I mean? The thing is, this game owns a huge part of it's success to the fact that BG1 and 2 exist and this is marketed as a sequel, if this were DOS3 in name and soul the game wouldn't be as big and famous as it is now or will be in the future.
So the primeval debate has always been: ''Is it BG3 a real BG or just marketing'' and I think the answer is something in between.