All I can say is: Larry Bird doing pilates and having a hyperbaric chamber post-game/his summers and analytics reports post game rather than putting cement in his driveway and drinking beer, or with tailor fit modern shoes for his foot and body type rather than chuck taylor cons all-star shoes would have likely:
A) extended the high points of his career. Thus his number of years with higher statistical proficiency and potential winning would have been 2-3 years higher at minimum than it would have been under the conditions he played.
B) he would not have radically changed in overall athleticism but his balance, footwork, etc may have improved and had been more agile etc., thus compensating for any generational differences in athleticism.
C)probably would have had a physique with more lean muscle due to generational differences in strength and nutrition. Thus, also compensating for any generational differences in strength.
D) in a more European ball centered generation he may have even slightly improved his scoring numbers in itself even after taking into account nutritional, technological, strength, and analytical differences by generation.
Also, older players (80s and 90s) who would have benefitted and likely been the same or better with the advances mentioned above are too many to name:
Dominique Wilkins, Tom Chambers, Clyde Drexler, Mitch Richmond, Chris Mullin, Dennis Scott (would have been lethal in modern game and with improved benefits mentioned above), Glenn Rice, Grant Hill, Dr. J, Kevin Mchale, Reggie Miller, JR Rider, Dale Ellis, Damon Stoudamire, Alex English, etc.
Or many, many other guys who weren’t hall of gamers (like some on the above list) who aren’t as well known if you’ve only been following the modern game and depend on the internet and propagandist mythology for remembering who was or was not good.