i think the point is, banning tiktok just means influence can move to these other platforms via other means (troll farms etc), it doesn't solve the issue (unless you want to ban twitter et. al)

but perhaps i am missing some obvious point?

There’s a distinction between adversaries trying to cause trouble within American companies and a foreign hostile government effectively owning the company and dictating policy in its own interests.

if they were forced to divest from bytedance would that be satisfactory?

Probably? I think that was one of the options iirc (ownership by an American company via a sale), but I don't really know enough about the specifics to have a strong position on the implementation.