Yep. Technically Thoma is a combination of Xingqiu and Xiangling but is just strapped with dog shit scaling which is what makes him bad. Piss poor damage, lengthy E cooldown with no Sac Sword to help it, standard ICD that's not good enough for vape or drive (but still steal vapes from the DPS he supports), reliance on keeping an 80 energy burst up 100% of the time to be useful. Thoma essentially combines all of Xiangling and Xingqiu's weaknesses with none of their upsides.

Scaling is as important as mechanics. If you take Bennett, nerf his atk buff and heal by 70%, increase its energy cost to 80 and double his E cooldown, you would end up with a unit that's as equally useful as Thoma. Even if he can do everything, he won't be able to do anything well.