Thats why I always bring in the 30th birthday when we compare across the decades the most dominant players
Top 5 most dominant players at a Slam on their 30th birthday (end of prime)
01. Nadal at FO - 9 French Opens (in 10 years)
02. Sampras at W - 7 Wimbledons (in 8 years)
03. Borg at RG - 6 French Opens (in 7 years)
04. Federer at W - 6 Wimbledons (in 7 years)
05. Djokovic at AO - 6 Aus Opens (in 9 years)
So it is safe to say that Sampras was the most dominant player at a pet slam until Nadal raised the bar, on the other hand Federer/Djokovic could not raise the bar in their primes, it was great age shift which helped them later on. Everything else won after touching 30 is great age shift, it does count but it also comes at the mercy of next generation players who are a decade younger and plenty of other reasons too.