how is it?
Fed had to get his RG title during the era of Nadal - the GOAT claycourter of all time
Agassi got his wimbledon title before Sampras Wimbledon domination began as well
More impressive in the sense that Agassi had to contend with a larger difference in conditions, play-styles, etc when he completed his career slam in the 1990s.
I guess you could argue that the field is stronger now, and therefore it is harder to win majors in that sense. But that's an argument I don't want to get in, as I think it's futile to discuss it.