Or they are counting bots and other ai agents and ignoring the truth?

Ultimately advertisers want a return on their spend and it's a closely watched metric for marketers. Them continuing to spend is indicative that there's growing value in ads, ie bots/ai agents cannot be the reason for their growth.

You could argue fb and particularly twitter are incentivized to include it in their DAU counts but market cares more for revenue for large companies.

"There is no alternative"

I wouldn't put it past Google/Meta coopting corporate advertisers. Everyone makes everyone look good, by stating the best possible numbers.

Google and Meta literally represent alternative advertising products.

So do Android and iOS. They're still the primary indicators of the strength of the smartphone market. You probably can't imagine a world without advertisements or smartphones, but that's the point from the post you're responding to that you're missing. If the advertising industry looks healthy, it helps everyone by keeping investors satisfied and share prices up, even if it's a ruse. It is possible for smartphones and the concept of advertising to cease existing some day. There's a spectrum between the current reality and absolute zero, and staying as far away from zero is the goal, even once we enter an inescapable decline.

Arguably true, but that's a rather different point than "there is no alternative". There are arguments to be made about market "health" and the relative sizes of the largest players, but what the upthread comment was doing was resorting to "anti trust" shorthand that clearly doesn't apply. There may be problems with this market, but lack of competition isn't one of them.

SMEs spend a lot on advertising, in aggregate. These smaller businesses are more sensitive to lowered conversation rates and will bail early - Meta took a huge hit in earnings in the aftermath of Apple's privacy changes due to poor conversions. Advertisers didn't keep pumping money in - they stopped campaigns.