Moondruid's greatest multi-class options in 5e are Paladin, Barbarian, or Monk. All of which don't work in BG3.
Barbarian - You can't Barbarian Rage while in Wildshape and if you do so before you Wildshape you don't get the full benefits of it. As well you don't benefit from Unarmored Defense feature from the Barbarian despite not wearing armor.
Monk - You can't benefit from unarmored defense as mentioned with the Barbarian which makes no sense since you don't have armor and do not benefit from armor worn while wildshaped.
Paladin - You can't smite while in Wildshape. Smiting is not casting a spell. Why is this a thing? Smiting with this multi-class is the single best thing you can do with your spell slots while Wildshaped.
Concentration Spells - It isn't casting a spell to activate one you already have concentration on. Making Heat Metal not be activatable as an example in Wildshape further limits Moondruid.
Then in general the fact you don't benefit from basically any of your worn equipment passive magical benefits....even gloves that give an unarmored bonus as an example.
So if multi-classing is terrible for Moon Druid and you can't make meaningful upgrades with Equipment AND you can't use spells you already have concentration on (all of these things being things you can benefit from in traditional D&D 5e) then all you have is the base wildshape making it the single most limiting subclass in the game. This is disheartening as Larian did such a wonderful job with the Owlbear appearance.
Please Larian. Right this massive mistake before moving on to greener pastures of other games.
