I'm not sure why anything I said is wishful thinking. Sure the game has changed---and we're not talking about 25 teams and 300 players overall, we're talking about a handful of specific players. What, specifically, suggests to you the exact players we are talking about here demonstrate the traits you are suggesting are true about speed and quickness overall? That's the question here.
In terms of matchups, as I said initially, Curry would score a lot of points on switches, obviously. But that's true of today, too. My point is that the specific matchups with DJ/McHale is a pretty good one to limit Curry somewhat (and as noted, to degree Warriors set up Parish or Bird that's less good).
Ultimately, the game is played at both ends---the Warriors would have a huge amount of trouble matching up with the Celtics at the other end as well--the four best bigs in the game are all on the Celtics--so they'd need a pretty huge effort from Curry to win these games. Which they could get, but which is about individual matchups, just like the NBA always is.
Since this is an imponderable, all we can look at is numbers, really. A couple people who have done so seem to suggest last year's Warriors team (which is obviously not as good as this year's) is hardly in a different league than the 1986 Celtics. I acknowledge these things are imperfect---but it's all we have
Kevin Pelton looked at last year's Warriors and put them 15th all time---the 86 Celtics were 2nd.
http://espn.go.com/nba/playoffs/2015/insider/story/_/id/13000418/nba-finals-where-golden-state-warriors-rank-50-greatest-nba-teams In terms of era and strength of opposition, Pelton notes " Boston dominated against a league that was nearly at its peak in terms of level of play" This year's Warriors team will rank higher for sure.
538's Neil Paine used a different system (SRS) to conclude last year's regular season Warriors were 7th best ever, the 1986 Celtics 10th...and in the playoffs, last year's Warriors were 8th and the 1986 Celtics 5th. He acknowledges it's close between those two in aggregate.
http://fivethirtyeight.com/features/the-year-of-the-warriors/ This year's Warriors will likely be higher using his approach. Intererstingly, his top team is the 1971 Bucks, so the conclusion there really isn't that 'new is better' either. His approach has some odd results (the 1986 Bucks as 11th best regular season ever, with 57 wins, for example)
Just to be clear, the Warriors are a ton of fun to watch and part of a changing overall NBA dynamic. But that dynamic isn't necessarily better, and it in part is driven by a reality about the challenges of getting quality big men today. That makes it more appealing to play small, but it does not mean teams with great bigs can't win. The Warriors vs '86 Celtics is harder for people to envision than (say) Warriors vs 96 Bulls because the team construction is so different---which (like the other questions noted) is different than the answer being obvious.