Nah, you can apply one eyed thinking to any era (“Fergie largely had a free run in the 90s when their biggest rivals the RS declined...and he only had to face such managerial heavyweights as Roy Evans, Kevin Keegan and Bruce Rioch as opposed to Jurgen Klopp, Pep and Mourinho”). Fact is United won all those titles in the 90s...did nowt in Europe mind (besides Bruce, Pallister and co. getting their backside handed to them in games by the like of Romario and Stoichkov). The RS were the best at home and abroad.
A decent appointment and the RS challenge for everything in the 90s. Beardsley, Houghton (who in Giants Stadium gave me my greatest sporting moment in ‘94), McMahon, Staunton and co. discarded, replaced by Nigel Clough, Paul Stewart (god bless him after what he’s been through), Mark Walters, Julian Dicks...Souness changed the winning DNA overnight, and bought badly to boot. It needed fine tinkering, not a mass clear out.
Ultimately, Souness took a mallet to a problem that required a chisel.
Moyes has similarly been a wrecking ball to United, discarding the back room team, changing the style of play to an expensive version of Wimbledon with Fellaini at the heart of it, and removing the aura the club had built up and instilling fear into a previous group of winners. The two biggest clubs in the country have had a very similar experience. It took the RS three decades to fully recover, United are closing in on a decade having yet to do so.