We implemented our player on top of video.js, and most of the developers who were there at the time still have nightmares about it.
We finally got the thing working, looking good, embeddable, reasonably cross-browser. We shipped it. A few days later, we get a curious email from some ad provider. "It looks like your VPAID ads have stopped running!"
Oops. We'd naively believed we could live without Flash (I take full responsibility for this stupidity). The sales folks pointed to a big gap between our old projected revenue and our new projected revenue. So we went and did the work[0], hating every minute of it.
The underinvestment in ad-tech by publishers and the cancerous ecosystem of vendors that have grown up around it is one of biggest collective mistakes made by an industry.
I am optimistic that this problem can be solved, and we are actively looking at this at my current employer. We sell direct, usually without a ton of intermediaries. Talk to me if you want to know more.
Incidentally, if you want to know if a publisher is going to survive the next five years, a decent proxy is the number of intermediaries involved in their ad supply chain.