During the 90s, a baseline player winning wimbledon was just something almost impossible to even suggest.
Even in previous decades, it was very rare (Borg and Connors were baseline players, but at Wimbledon both did serve-and-volley a lot on first serves, and both ended most of the rallies at the net; Lendl was close to win Wimbledon, but Lendl did serve-and-volley on all his first serves and many second serves, and he had a great serve).
Agassi's serve was very mediocre, and his volleys were very ordinary too.
He was the first player to win Wimbledon with just his return and groundstrokes.
Again, it was nothing like today. In the 90s, it was so much faster and the bounces so irregular, that a player winning Wimbledon having a very ordinary serve and net skills....was impressive.
It is impossible to compare different eras, but if I had to bet, I would say that neither Nadal nor Federer would win Wimbledon from the baseline in the 90s (had they been born 15 years earlier I mean) like Agassi did.