Humor and/or weirdness = Yes. Whimsy/silliness = No.
One or two demon lords + the Underdark = Hell yes! ALL the demon lords + Alice in Underland = Pass.
Demonically-possessed slime monsters = Sure. Pudding Kings and talking mushrooms named "Something-dump" and "Stool" = No bueno.
Edit: My opinion, obviously. But as much as I REALLY like the 5E rules, the product line otherwise continues to miss the mark for me. Gimme something serious, gritty, nostalgic, original or epic (pick three), not in the Forgettable Realms, that doesn't misappropriate a story line from another beloved campaign setting, and I will happily throw some bucks to Wizards.