I hope this doesn’t come across as an insult as you’ve already expressed your dislike for Outbrain and Taboola but you’ve stepped right into their market and have a huge opportunity to shake things up.
I’d say you’ve figured out what every publisher loves - or should love - keeping traffic and keeping the audience engaged. I assume most smaller publishers >10m views would make more money keeping readers clicking around their own site several times compared to losing them to a “click-bait” sponsored content ad.
I would however recommend after spending a decent amount of time on your site to take a look at Taboola and Outbrain - the copy and design of their sites are very to the point and informative - to publishers and advertisers. I don’t really get that from your site. I’d try to be more like them in those areas - they have a knack for grabbing both publishers and advertisers.
As for getting the advertisers, get on LinkedIn - search for people with job titles like Manager of Digital Marketing - poke around their profiles see if their company might be a good fit for you then fire them off a quick email.
Just my two cents!
In which case they'd have to figure out how to look for "related" content to sell. However affiliate programs like Amazon's for one example definitely seems like a good suggestion.
You can browse through the inventory of similar sites to get a gauge of what you can expect, CPM wise: https://buysellads.com/buy/allsites/
Later on, you might just want to strike one-off deals with interested advertisers, or build in a more "native" ad solution into your platform, etc.