While I wouldn't mind seeing first-party ads, with the way that businesses work I think we'd get stuck in a cycle:
1) sites have ads from third party services doing all sorts of yucky stuff
2) Users complain about ads, ad revenue drops due to blockers
3) Site moves to first-party ad serving and vetting, ad revenue increases at least some-what
4) An MBA or someone from marketing (probably a VP) says "Hey, we have this great, trusted ad-serving platform for our own website(s), we should let others place our trusted/vetted ads for a share of revenue"
5) As more third-party sites adopt ad platform, the advertising arm is either spun off, or the company sheds all non-advertising areas
6) Ad platform grows large, and in the Quest for More Money, downsizes the department that vets advertisements and makes advertiser submission more automatic
7) GOTO 1
Some sites might be able to freeze at 3, if they can avoid MBAs and refuse to let marketing take the wheel, but for most (especially if they're bought up by larger entities) the cycle will repeat.