While experimenting with Gatsby + Drupal and doing research for my previous posts here, I came across the GraphQL Twig module.

This module is beta and hasn't had a lot of activity. I'm not sure how it addresses some deep Drupal theme issues, but it presents an interesting idea:

"The GraphQL Twig module allows you to inject data into Twig templates by simply adding a GraphQL query. No site building or pre-processing necessary."