Personally, I'm not a huge Vercel fan (IMO: lots of hype, business model encourages developer ecosystem lock-in), but this post gave me more trust in the design/UX care that goes into their products (which is a core Vercel strength).
If that doesn't alleviate your concerns or you disagree, I'd love to hear your thoughts about how we can improve
Personally, I don’t bother with nextjs at all.
A Next.js project can be deployed to a Docker image very easily [1]. If you want to use a provider that has their own infrastructure setup, then yes you need to do some work (that OpenNext does for you). But that's true of practically any framework deploying to a host that does more than just serve the docker container.
You might want to look at the comments in this thread [1], to get a feeling of the "accusations", as you want to call it... I'm not "accusing" anything, I really couldn't care less, I don't use Vercel/Next.js and never will, but maybe you should read the linked thread, too see how people (at least on HN) see your company.
No single entity should have that much power, especially no venture-capital backed one.