You can work around this with some Workers that capture the dynamic routes, request the nextjs html file and return that, but then you're using up your Functions quota as well.
I have found that with Cloudflare's documentation that where it's lacking they have the ability to PR in changes and if you go back to a saved page, I've found them pleasantly updated numerous times.
Thankfully the cutting edge development is based off of open standards that you can easily build off of. I know personally that I've found most of the sticking points of developing against Cloudflare to be easily mitigated and just be an overall better experience as a customer than with another hosting provider.
It doesn't hurt that they aren't charging me all that much personally, but I have a day job that fills up the Cloudflare stock price just fine.
Their docs are subpar because Cloudflare is just not interested enough in documentation improvements and is hostile to the people who are interested and who try to make the improvements.
I tried fixing a 404 in their docs once. This would have taken, you know, approximately 2 seconds with a real wiki or CMS[1]. What resulted instead was an excruciating back-and-forth that took 9 messages over a span of exactly 5 hours, ended in no fix, and a Cloudflare dev trying to "upperhand" me (in the vein of George Constanza's pre-emptive breakup—"I'm afraid that I am gonna have to break up with you"[2]).
Sure, Cloudflare team, there's nothing wrong, I guess, with choosing to believe in the delusion that a repo full of Markdown files and the GitHub generation's busted-ass PR-based edit workflow is an acceptable substitute, just like there's nothing wrong with writing your name with a pencil that has a brick taped to it[3].
1. <https://groups.google.com/g/mozilla.dev.mdc/c/BU09C48bmGU>