Part of the reason these teams are shooting this many threes in the first place is lack of efficient post play.
The 2000-01 Lakers shot less threes than every single team in the NBA this season except two. You don't need to shoot threes when you have a dominant big man that will score on nearly every possession when he's in the right position.
Case in point is the 2004-05 Spurs that literally made the LEAST threes out of any team in the league that season, and they went on the win an NBA Championship. What those two teams have in common is dominant big men - Shaq and Duncan. The 90's era Bulls did not have a dominant big man, but they did have the greatest NBA scorer of all time, along with elite wing defense (as did the Spurs with Bowen).There are no dominant big men today that are going to get you points in the paint and mid-range like your Robinsons, Olajuwons, Ewings, Malones, Barkleys etc were able to. The likes of Rik Smits would be a multiple-time all-star today based on statistics. At the end of the day, when the pace of the game is slowed in the playoffs and teams get into their half court sets, team defense becomes the most important aspect of the game. In that regard, the 90's Bulls would smother Curry's Warriors. Curry and Klay are good perimeter defenders, but they are no Jordan and Pippen. Draymond Green is a good role player and workhorse, but he is no Rodman. None of these 2010 era teams would know what to do with a Prime Shaq. The Grizzlies are the closest thing to a 90s era team, and they have been very effective in this era, but lack a dominant scorer - or any scorer for that matter. If they had just one, they would be a Championship contender.
That Seattle Supersonics team that you've listed is pretty solid, and would give most teams in the league today a run for their money. The Knicks team you listed held opponents to 95 pts/game that season, you should really frame some of these points in the right context. While I will agree with the OP that spreading the floor with good perimeter shooters has revolutionized the game somewhat, it doesn't necessarily mean that it is now superior (perhaps offensively it is). These teams still lack the post presence that would force their opponents to double on their dominant center and make their defense collapse.Teams from the 90s had inferior shooting on the wings, but they did have superior post play and defense and the greatest teams have usually been built on that. I guess I will disagree with the premise of this thread, and chalk it up simply to it being a preference for eras. But I am not seeing anything convincing enough to conclude that teams in this era are better than teams from the 90s.
As for this whole nostalgia debate in sports; no one has any problem calling Manning and Brady the greatest QBs of all time or Messi the greatest soccer player of all time, or Federer the greatest tennis player of all time. I think people genuinely feel that the 90s were the golden era of basketball. It's an era that was stacked with Hall of Fame greats and not one where James Harden is a consensus top 3 player in the league.