Its not a myth at all, I did some research and analysis on it in another thread last yearI think it’s a bit of a myth that modern players cover more ground than players from previous eras.
You can argue pressing and transitions, may have evolved, the overall physical output in terms of distance covered hasn’t drastically changed.
Players are far more protected these days so you could say the physical toll is also a lot less than it has been. It’s also worth noting that modern pitches are generally in better condition
The game might look faster today, it doesn’t necessarily mean players are working harder overall.
The average professional football player now covers about 60% more ground, plays almost double the amount of games (if international and european football calendars are taken into account) and makes about 40% more sprints / hi intensity actions per 90 minutes compared to a player from the 80s.