I’ve been on Threads since Gaza, October 2023. I’m a regular, daily active user. I have seen virtually zero ad posts or obvious bots. It’s not zero to be sure - but let’s say in 13 months I have seen an average of 100 posts per day (just a rough guess) including replies. That’s approximately 39,000 posts and I bet less than 50 of them have been ads or obvious bots.
It is true, however, that Threads mutes posts - and there’s a button I can press to see the muted posts, but I never press is. Perhaps that’s where they are. But my last months at Twitter were seeing a healthy percentage of that kind of activity