Exactly that, the market is skewed by monopolies. You can easily setup an ad server, but good luck getting the attention of an advertiser. Google has a stronghold on display ads, almost a monopoly.
That's a demand problem not a monopoly problem. You can't get advertiser attention because advertisers have limited interest in advertising on small scale properties because it's not a scalable way to do business.
If anything Google provides more opportunity because the alternative to AdSense existing would probably be no revenue at all for small web properties.
Exactly that, the market is skewed by monopolies. You can easily setup an ad server, but good luck getting the attention of an advertiser. Google has a stronghold on display ads, almost a monopoly.