Really Command and Tasha's Hiedous Laughter have really changed the game when it comes to multiclassing. It used to be that multiclassing a full caster meant losing substantial power WRT high level spells.
A 11 Cleric/8 Wizard/1 Ranger or 11 Sorcerer/8 Cleric/1 Paladin are substantially weaker in 5E than a single class Cleric or Wizard. Now with Command or THL they are ahead of a single class character in most encounters.
Command or THL upcast is usually generally powerful than most higher level spells if you have the number of enemies to target and the extra versatility you get with multiple spell lists, twice as many Cantrips, martial weapons and mastery while not losing any slots is a big boon.