There’s also a different side of the story: UI are very pricey to get right — that’s because user research is not cheap — so a very efficient approach is having disposable UIs since you know you are going to get them wrong at the start.

Carefully designed endpoints require a lot of back and forth between teams with very different skill set so to build them you need to plan in advice, but it does not work here where you literally have to move fast (and fail fast!).

You only have two options left: (1) you either ask frontenders (or UX-wise devs) to do the whole thing or (2) you build an abstraction layer that let frontenders query arbitrarily complex data structures with near-perfect performances (YMMV).

In case (1) you’re looking for REAL full-stacks, and it’s not that easy to find such talented developers. In case (2) well… that’s GraphQL.