I know that I'm simplifying (probably too much), but it seems like things were fine when GitHub was still a Ruby on Rails monolith and all the rigmarole with microservices etc. only made things worse.
I’m sure survivor bias is at play here, but when I look through the older code bases - especially the data model - it’s an entirely different world than the newer stuff, and it’s clear which of the two was written by people who understand systems.
Or, it would require an architect who has a very good understanding of the system. Which in reality seems to be rare.