I myself directed teams of developer up to 35. Do not know beyond that scale. Teams simply worked on modules and main designers made sure they complied to a shared interfaces / state machines in more complex cases. Not a big deal. The law was: I trust developer so here is your module interface and constrains. Now go away and come back with implementation (which would still compile to a single monolith). As I was lucky to work with very good programmers bar couple of bad apples I've never had any real problems with the delivery and its quality
Its clear that you could afford to not use microservices (which is great! You didnt burden yourself with the cool approach since it wasnt necessary). Not everyone has those requirements though and may NEED them
I completely fail to see what is so "cool" about increasing system complexity beyond of what is actually enough for most of the real life cases. To me: reliably working product is what is "cool" and that is what I've always pursued.
