> don't want to build in a language w/o types

Yep; that's the only reason I don't use Rails.

I'm building "ActiveRecord but with type(script)" at https://joist-orm.io/ and have our own internal "kinda Rails w/GraphQL" going internally--so far we're at ~450 tables and still "feeling good" (no n+1s ever!), but definitely a long way to go before AirBNB-sized problems.