That’s always been an issue. Years ago, researchers demonstrated in an experiment that they could swing public opinion about electoral candidates by manipulating search results. Who knows if Google took that experiment and ran with it?
Widely-used platforms that can +/- 1% their algorithms to affect democracy have pretty high burdens of trust/transparency, and we're not close to that with any platform (Chinese or not) that I'm aware of.
Meta's probably the closest, because of scrutiny, but afaik even their transparency isn't sufficient for realtime attestation.