I consider it a design error if there's ever a level for a class that you don't mind losing. Multiclassing should always be an agonizing decision between the classes.
Well, meaningful, at least. I like multiclassing so I’m cool with half and half builds being not super painful.
But it should always be a trade off.
I actually wish it was less painful in some cases. Like, extra attack makes martial multiclassing super weird, and there is no equivalent to the softening of MC woes for casters by using the MC spell slot by level table.
I wonder again, after years of not thinking about it, if true multi-class feat (with 2-3 per class) wouldn’t be a boon for the game. Especially if those same feats could also be useful on a single-class member of the class it’s a mc solution for.
Eg, 3 feats that give you a little bit of low, mid-low, and middle, level rogue features, but does so in a way that also benefits a rogue character that takes the feat.
Spellcasting feat chains to get spells above 2nd level from another class, would also be good. An Extra Attack feat wouldn’t benefit martials, only kinda-gishes that aren’t gonna get it in thier normal progression, but…I wouldn’t hate seeing that.