You accumulate web frameworks and maintainers similar to the winning strategy at Monopoly, until you have implicit control over entire ecosystems. Whether you actually seize that control or not doesn’t even matter, because you are in a position to do so—by strategic neglect, or increased attention to whatever project supports your current business goals best.
No single entity should have that much power, especially no venture-capital backed one.
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.
I think the fact that OpenNext can exist speaks to the opposite
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.
