I'm not sure if anon is asking about lore-wise or gameplay-wise.
Lore-wise, I think kaveh is strong! He walks miles across sumeru to the desert to visit his construction sites and carries mehrak (which is an ancient MACHINE) everywhere, I think mehrak's weight is very heavy. I don't think he's a dainty person who only draws in his room, not getting sunlight and all... He's not weak even if he's not the strongest.
If you're asking about his gameplay, I'll say he has limits, well, he's a 4 star, but I think no character is a weak character if u build them correctly with the right stats ;D I always remember the guy who plays dps Barbara hhahahaha XD it proves that no character is really weak or useless. I've heard about his leaked kit works very wonderfully with a full EM+ER build with nilou!