I know this comment is old but can you elaborate on this? I always see the sentiment around Reddit/Lemmy but so far I haven’t seen anything bad other than the CSAM scandal.

The only thing that comes to mind is app telemetry, but that’s easily disabled. Personally, I have macOS show me crash logs so that I review them then decide if I indeed want the developer to have the report.

Reviewing DNS queries (I’m big on blocking ads/tracking via my DNS over TLS server) I see tons of requests for Google services coming from apps, so I’ve blocked every in-app tracker I can find.