Warbringer
Explorer
There are a lot of people who would take issue with that assessment. I found 3e multiclassing to be generally better with the exception of dealing with spellcasting. In 1e/2e, multiclassing as a spellcaster was usually too good with PCs gaining most of the benefits of being a fighter and a wizard only 1 level behind (in both) compared to his single-class companions, while in 3e multiclassing with a spellcaster was generally too weak.
So only a small exception then

As there is still no unified source of "magic" in 5e we are running headlong into the same situation. By unified I mean that "combat" is unified in that everyone has a BAB equivalent and hit point die with an feat like system into weapon and armor proficiencies. Magic needs a mirror to this to a a fluid multicast system:
MagicBAB, dice based mana system (sum of which could determine spell slots for vancian system, straight mana for power system), and spells/schools/domains as proficiencies ....
That's my take, FWIW