I've not honestly done a "all classes" run since ARR and back then, the cross-class system - assuming you put the work into it - was far, far more robust than the role system could ever hope to be. So while you were missing some powerful abilities or spells, the sheer diversity in your toolkit did help to make what you lost seem less harsh. This was a little over six years ago, however.

Since that time, what a class actually gives you has been trimmed and removed overtime to the point where it's laughable what you actually acquire from classes today. Today, going into 50 content as a class leaves you worse off than it did six years ago. Going into anything beyond 50 as a class is far, far worse.