I think the biggest issue was the European ban as it took a few years for English teams to be competitive in the EC again. When you stop playing against the best, your standards fall, and five years out of Europe set English teams back a lot. As well as not playing against the best, so many top English players left for the continent: Gazza, Waddle, Hoddle, Lineker, Platt, (Des) Walker. English domestic football went backwards.
United losing to Galatasaray and even Gothenburg gave you the runaround, so it wasn’t just Barca that rinsed Pallister, Bruce and co. Didn’t you lose your unbeaten home record to Ferencvaros (sp?). If I remember correctly I think you did. Not even the top sides were beating United in the Champions League. It took a good seven or eight years before English football was able to compete at the top table again, culminating with “And Solskjær has won it”.