"There, done."
Except, we're not done.
YAML has multiple footguns like this, which I have to remember, forever. And anyone who works with YAML. It's unintuitive and confusing, and costs space in my brain that I really should be using for more important things.
Not to mention that if you -don't- know about these ahead of time, debugging them can be confusing.
A type system is marginally more work for decreased cognitive load and eliminating stupid, idiotic bugs that nobody should have to waste their time tracking down.
With IDE integration, the cost is pretty much negligible other than learning the syntax, which, c'mon, is not difficult and we're being paid to do it.
There are even tools like Dhall [0] that auto-generate yaml for us.