Yes, Seth is bottom tier.
Low damage output
No defensive options outside ex 623 super
Mix-ups depend on teleport gimmicks
Normal moves are terrible as in has small hitboxes (This game favors characters with moves that have giant hitboxes and fast recovery, I.E. Gord, Wald, Merk
Lowest health in the game (He literally dies in 2 combos.)
Terrible neutral game. Segment can only take you so far.
Impossible to get in against zoning characters, Hilda, Vatista, and Yuzu to an extent.
And the list goes on.
Honestly if you're new and still learning the game, just pick Gordeau he's easy to use and will teach the basics. He's pretty much the Ragna of UNIEL.