You say you've never understood the benefit of unit tests but you list three really great things: they help you debug stuff while you're writing it, they help you understand what you're writing and the edge cases, and they help others understand your code later. That's all great stuff.
I mean i was being in tongue in cheek, but it really seems like a "Why do you look at the speck of sawdust in your brother's eye and pay no attention to the plank in your own eye?" kind of situation.
The original "Monorepos please don't" article really just convinced me how great monorepos are when you aren't at scale. So you know, put your shit in a monorepo, and then when it gets painful, break it out.