I have a eloquence bard in my 5.5 that is working just fine right now. And I think that is part of the issue with blanket statements. Sure, the storm sorcerer is ass compared to the 5.5 sorcerer subclasses, but the twilight cleric didn't become outclassed by any 5.5 cleric domain (even stripping the weapon and armor profs from the domain).
As a rule of thumb, I find anything post Tasha (Tasha, Spelljammer, Planescape, MotM, Strixhaven, Dragonlance, Bigby and Fizban) "good enough" to run in 5.5 without major changes needed, while pre Tasha stuff (Xanathar's, Wildmount, Ravnica, Theros) may need a lot more work. (SCAG, Rising from the Last War, Van Richten's Guide, Tome of Foes and Volo already have been replaced with products with updated mechanics). That's still more stuff than not. So outside of Xanathar's having weaker options and the few settings needing updates, I don't see a pressing need to ban 5.0 from the table.
Seriously, D&D doesn't need to be solved with strict meta builds and tier lists like it's a dangerous MMO. You will do just fine adding college of swords to a 5.5 bard...