There are some community solutions cropping up for the Data API (see discussion at Data API and HTTPS Endpoints are Deprecated? - #14 by Sven_Glockner).
I haven’t validated any of these personally, but there would definitely be options to explore that don’t require a subscription.
If would be amazing if you can report this to the issues channel on github as advised in the blog post here: Sign in to GitHub · GitHub
I’ve opened 🐛 BUG: `mongodb` can be imported but not successfully used with nodejs_compat_v2 · Issue #6684 · cloudflare/workers-sdk · GitHub to continue tracking this issue.