I've also never seen a single character that can do all the things people claim. A dex based fighter can make a pretty decent rogue replacement for example. On the other hand a wizard casting knock only works if you ignore the sound that can be heard 300 feet away. Just like they ignore the downsides of charm person and several other spells.No, not in practice thst I've ever seen. The DMG describes how to set up a full dungeon thst will push a party. If anything less is done, things get a little wacky but will still work just fine. But if a table feels there is a caster/fighter imbalance, that is a symptom of the party needing to be pushed harder. Simple as.