They said they might add it. You unlock cosmetics in solo but you have all the cards. Solo isn't the same as playing with bots (but I wouldn't trust bots on Veteran), in which you can unlock cosmetic stuff.
Personal preference, I don't know why someone would play a game built around coop solo unless for the challenge (I get when you might have to play offline, though).
I don't know if the game is worth $60 since similar games are $10-20 cheaper but it's great for Game Pass.