I don't mind a bit of multiclassing, to be honest, although I agree that splashing in 5 or 6 classes gets exhausting.
5e limits this to some extent by placing level up rewards deeper into the class:
ASI/Feat are awarded every four CLASS levels (not character levels). Multi-attack requires 5 class levels (no BaB stacking for multiple attacks). Higher level spells require you to stick with a class (although spell slots do not).
Pathfinder does this a little bit, but a lot more stuff is front loaded (1 level of monk gives wis/cha to AC + a free feat for the most egregious example).
I think 5e has the same issue, one level of monk or barbarian also gives you Wis or Con to AC (Plus dex) by means of unarmored defense. And the way D&D5 is made, a 20AC plus armor is much more difficult to beat than in pathfinder 1e and 2e (you have more ways to improve your %to hit besides getting advantage)
And barbarians can use shields with unarmored defense, could pick the bear totem that halves any damage besides psychic, etc... so it is even worse.
Also, if we can talk about the common dip with one level of Warlock that gives you the best damaging cantrip on the game, eldritch blast (that improves with character level, not with class level so you can use it up to level 20 without penalties), and the hex curse at level one, one of the best ways to reliably add damage for 8 hours (if an enemy dies, you can pick another target to curse so basically you can do it all the time, since its a bonus action); and some other patron feature. I level of warlock has something that is useful for all classes. Yes, you heard well, all classes.
Since the last feat/ASI comes at level 19, not 20, there is a meme about why this is: So all classes could pick a level in Warlock.
