Zardnaar
Legend
My online 5e game doesn't use feats; it certainly works fine (PCs are 10th-13th level). Compared to my tabletop game which does use Feats, the PCs generally seem to have reduced damage output, but more durability from their high stats.
BTW I don't use the multiclassing optional rule in any game, it seems far more problematic than the feats. I can't see any reason to allow MC but disallow feats.
Allowing multiclassing but no feats is kind of an AD&D vibe.