Having seen a large org attempt a poly -> mono repo conversion project (which took almost 2 years and failed and was in the process of being rolled back when I left) I agree with everything in this article

Once an org becomes large enough you need lots of custom tooling to make working across a huge codebase smoother, and that tooling is similar for mono and poly repos, but you need an additional metric ton of tooling to make monorepos work

And please pray you didn't decide to go with bazel for builds

My least favourite monorepo experience: I want to update my dependency for my tiny service for a security patch -> Oh, 400 other services depend on it and dozens of tests break when I try to update it -> this isn't worth my time I'll do something else instead

We were promised a world where every dependency was kept up to date by necessity but ended up in a world where all dependencies atrophied due to the increased difficulty to update them