Of course the recent Warriors team have put their stamp on the game as 3-point specialists. I have to say, though, that all three of the teams selected so far as "Best NBA team" would be able to adjust a good bit to today's game.
The 95-96 Bulls and the 85-86 Celtics both had at-the-time elite 3-point shooting. Everyone (that's middle-aged
) remembers Larry Bird being good behind the arc, and probably a lot of fans remember Steve Kerr being deadeye from deep and Michael Jordan being no slouch himself. But both of these squads had four legit 3-point weapons on their rosters, some of whom would see hugely increased minutes in the modern game.
3-point shooters used to kind of be like specialists ... not really guys you would build an attack around, but guys who could come in for a spell and disrupt the flow of the game to his team's advantage. For the 1986 Celts, they had not only Bird knocking them down from deep, but also Danny Ainge, Jerry Sichting, and 2-time All-Star Scott Wedman. The 1996 Bulls, similarly, had four sharpshooters: Kerr (led the NBA at 51.5%!), Jordan, Toni Kukoc, and Jud Beuchler (Scottie Pippen attempted plenty, but was less efficient than those four).
What would've changed a lot for those older teams playing in the modern era was their bench rotations. The 1996 Bulls would've used a lot less of Ron Harper (26.9% from 3) and a lot more of Beuchler (44.4%). And their trio of interior foul-collectors (Luc Longley, Bill Wennington, and Dickie Simpkins) would've been a lot less useful.
As for the 1986 Celtics, Bird and Ainge could've added more volume from 3 to fit in the modern game ... though their statistical efficiency was somewhat less than even the Bulls team ten years later. Sichting and Wedman were plenty efficient from deep, but didn't get near the volume that top modern 3-point shooters get. A long guy like Kevin McHale, IMHO, would still have a role in today's game -- he was ~60% from inside 12 feet during his prime, and I think that would be tick higher today. The Celtic who would really get left behind would be bench banger Bill Walton -- it just wouldn't be fair to ask him to chase modern 5s around the perimeter.