This is exactly what Shopify does with their monolithic Rails app [1]. I worked at a company with ~200 engineers that used the same general architecture and I really enjoyed it. We got a lot of the benefits (clear interfaces, teams able to work on their system without having to understand the whole platform, build optimization, etc) without any of the operational headaches that come with microservices.
[1]: https://shopify.engineering/shopify-monolith