That's not to say TikTok won't amplify what you engage with, it absolutely does but it's good at not showing content that makes you feel like shit. Obviously it does test showing new and different content, but it won't show people Fox News willy-nilly. Content can't be too far out of someone's interests. It also won't start an autoplay rabbit hole of conspiracy videos like YouTube does, you'll get your usual feed after the tests, there are plenty of chances to stay on "their side" of TikTok.
I too have very little sympathy vilifying one platform that optimises for content you like and then defending others that optimise for content you engage with. The former really letting people stay away from right-wing propaganda, the latter actively pushing everyone towards it.
While I cant't deny that that maybe something that could be happening, in my own experience, the more pernicious problem is the creation of filter bubbles where people only see and hear view points of those they already agree with and slowly get pushed into more and more extreme versions of their existing beliefs.