Guys PLAYED more physical because of the rules, some of them were heavier, they weren't generally stronger. As to the guys you mention... Luka is incredibly agile for his size, Jokic too, even Steph.. it's pretty telling that you picked 3 guys you think of as not great athletes, all of whom would be very good athletes in past eras... Luka is similar size to Larry Bird, he's much quicker and more agile, he jumps higher, he's stronger. Jokic weighs 30 pounds more than Patrick Ewing, and he's a more agile player, and not significantly worse (probably better honestly) in most other athletic categories. Guys have way better training regimines, they lift weights better, they eat better, they start specialized training earlier.
I watched plenty of late 80s and 90's games, you're mistaking athleticism vs. peer with pure athleticism... it's like comparing the 80s to Russell.. Bill Russel was the best athlete in the NBA by a good margin, he was an Olympian.... he wouldn't have been an Olympian in the 80s/90s and his level of athleticism would not have been the best in the league.
The NBA wings and guards of today are bigger, stronger, jump higher and are more agile than their 90s counterparts, this isn't even close. I'm not sure why this is controversial, we have TONs of evidence in every single sport, the Olympics, pre-draft testing, that over time athletes have significantly improved in every area.
Edit- I'd also note, the NBA was more "physical" in the past for several reasons:
1. Guys had less skill
2. Teams and players were dumb about the value of the 3pt shot
3. The rules were different
4. The league made less money so nobody cared what happened to those guys.
