NX with a Nest.js backend, and Next.js front-end. These tools just aren't very nice to jam together into a fullstack app. I'm really not a fan of NX itself. Lots of people love it, but I think it's way too much for most use-cases.

Furthermore, in our case, the front-end and backend are really coupled, so having these as separate systems is just a big headache. All of the web app's views are tied into specific backend functionality, and our API doesn't really stand on it's own without the front-end.

Yes this is poor architecture. I'm just pointing out a case where JAMStack was a mistake. Rails (or similar) would have been a smarter choice.