Yes, this is very good point. I believe there are two problems here:
One is technical, you are expected to be able to build the entire compiler/build tool locally before you can add something to the standard library.
One part of that is a bad analysis test that will fail if anything changed in the standard library. Another bad part there is that installing all the OCaml stuff can be very rough.
The other problem is governance, there is no good process to add new things to the StdLib. It kinda happens and might benefit some formal decision making process.
Yes, another good point. I fear there this repository is largely the work of one individual, so we should indeed focus on making it easier for others to step in.