I'm a Technical Director of a design/web agency (small scale, I still build one out of every 3 or so sites). We use Sanity + Next JS (or Sanity + Remix more recently) in a repeatable way. I used to use WP a long time ago, and even then I had my own setup to use twig templating, my own image resizing solution, etc.

I have been considering pouring energy into this problem or at least offering advice, our approach is definitely bespoke and not scalable in the way WP is, but I've long thought the middle ground is in need of ~something~.