Flails are just objectively worse than warhammers. Same damage die, but lacking the Versatile trait. I've played with giving flails some other sort of secondary ability but never found something that works.
Morningstars are functionally the same as warpicks, and both lack the Versatile trait. I've settled on changing the morningstar's damage to 2d4 split between 1d4 bludgeoning and 1d4 piercing to set it apart.
The weapon system in 5e is half-baked. It feels like someone put it in as a placeholder and never bothered to give it a second look.