I think it's pretty simple:

1. Ads are mind cancer.

2. The better a platform is at delivering ads, the worse it is for your mental well-being.

Point (2) is not just because of the ads themselves, but also all the incentives created by ad-monetized platforms. So much slop, misinformation, clickbait, and ragebait is caused by people fighting for attention to get that sweet, sweet ad revenue.

There's a reason "peak TV" happened after TV shows were freed from the need to bend their structure around several ad breaks. This stuff is not just a "monetization strategy", it infects the surrounding (non-ad) media and fundamentally changes it for the worse.

Edit: One last point - ad delivery requires taking control away from the viewer/user. A platform that's good at delivering ads is necessarily one that makes it hard to block/skip/remove the ads because most users would if they could. This same mentality of control then informs the rest of the design. So you have endless A/B tests you can't opt out of and "I'll enable it later" dialog boxes instead of allowing the user to control their experience.