Well you won the UEFA Cup in 1990 (back when it was still a quality competition), though Im not sure whether Alessio and Zavarov (who indeed was more of a flop than a fundamentally mediocre player) were still there.
I think Galia was a decent mid, a bonafide water-carrier. Hardly the worst player Juve had during those 7 years in the wilderness. He scored the winner in San Siro in some Milan-Juve of the early 90's and was even picked for the NT a couple of times if I am not mistaken.
To his credit, Marchesi had inherited only the scraps of Trap's cannibalesque Juve, but he also lacked in too many departments to coach a big team.
Maifredi on the other hand had quite a good squad. Well behind Milan and still inferior to Inter and Napoli, but his bizarre tactics prevented you from even grabbing a UEFA spot (until then, something unprecedented for Juve I believe).
Mastropasqua I basically only inserted because of the funny name.
I may have been a bit too harsh on Magrin as he wasn't that horrible and paid the price of being initially expected to replace Platini. Still not Juve material though.
Pacione is arguably the worst attacker I've had the chance to see play for you. Juve had bought him from revelation of the decade Verona after he had scored a double against you the year before. He played nearly every game in the serie A that season without scoring once, and beat the world record of missed sitters in a UEFA Cup tie against Barcelona which you should have won 6-1 but tied, thus going out of the tournament.
Buso and Traspedini were both affected by the "flash in a pan" syndrome. The former scored a hattrick against Maradona's Napoli aged 20, never to be heard again.
All in all, there may have been more mediocre players at Juve in the past decade than some of the aforementioned, but in a 25-30 players squad it's easier to do without them by just leaving them at home, whereas back in those days the more limited number of players a coah had at his disposal meant these guys would receive more exposure ergo more ridicule.