Yes. I worked on two large monorepos, about one quarter per project. Maybe 80+ devs on first, maybe 40+ on second. Both were not sure how to describe this but ultra-high-velocity agentic driven development efforts.
On the first, there were ~no shared skills. There were some requirements set up but they were not minded properly and became stale / ate context for little gain. The hardest hit was in E2E tests which would flake and create long running, too-often failing CI. People would disable them, because they were not reliable and velocity was so high, no one was happy w them.
I maintained my own set of skills and CLIs to back them. I'd share them if they came up but it was like the old days of manage your own stuff. Not much credit for building and sharing devex tooling to the team.
But then on the second one we were in better shape--we had vendoring set up to distro skills automatically.
Before the project was well underway, I put time into understanding how all of our tests aught to be written. Finding the forbidden things, etc, getting review from our best test folks and ultimately landed on a `/test` that routed across all possible test types.
Like night and day. Instead of finding out while trying to get a release out the door that some corner of the project had a handful of flakes, tests were written the right way from the start.
Like, it was beautiful. And I don't think devs noted difference while building. Only that there was an absence of BS in CI.
Hard to quantify the lack of pain, but it was big!