I always found it odd when people compare players from different eras. These days you have guys like Hazard that eat 2 burgers and can't keep up with the game anymore after that, while back then your average player spent more time in the pub than on a football pitch.
Different standards and it would be way easier for a player with a good mentality and training discipline to stand out from the rest back then.
But you can still do comparison in terms of how those stands out among others at around same era. For example, let’s look at top footballers/forwards playing in top league back in 60s or 70s
60s or 70s
Pele at 34: 10 goals in 27 games
Law at 33: 2 goals in 14 games
Muller at 33: 13 goals in 21 games
Eusebio at 33: 2 goals in 13 games
Steeler at 34: 9 goals in 25 games
Sivori at 33: 1 goals in 3 games
Fontaine at 28: retired
Kocsis at 33: 9 goals in 19 games
Kocsis at 34: 19 goals in 29 games
Kocsis at 35: 0 goals in 7 games
Then we only have 2 players which stands out at this age and beyond during 60s, overlapping with active period of players listed above:
Puskas at 33: 47 goals in 36 games
Puskas at 34: 44 goals in 41 games
Puskas at 35: 40 goals in 40 games
Puskas at 36: 31 goals in 39 games
Puskas at 37: 28 goals in 33 games
Puskas at 38: 17 goals in 25 games
Puskas at 39: 10 goals in 14 games (retired)
Di Stefano at 33; 23 goals in 34 games
Di Stefano at 34: 30 goals in 36 games
Di Stefano at 35: 22 goals in 41 games
Di Stefano at 36: 22 goals in 24 games
Di Stefano at 37: 17 goals in 34 games
I don’t think we can simply put it all down to different standards in different era. To stand out at that age back in those time is as difficult as to stand out in current time. Puskas and Di stefano is just like Ronaldo and Messi approaching their mid 30s, in terms of how they stand out among others at similar age:
Ronaldo at 33: 44 goals in 44 games (50 goals in 51 games including international)
Ronaldo at 34: 28 goals in 43 games (42 goals in 53 games including international)
Ronaldo at 35: 37 goals in 46 ganes (40 goals in 52 games including international)
Ronaldo at 36: 36 goals in 44 games (37 goals in 47 games including international)
Messi at 33. 31 goals in 44 games (36 goals in 54 games including international)
Messi at 34: 38 goals in 47 games (39 goals in 51 games including international)