Seems like a lot to set up, especially since all you really need is "cat ~/.ssh/config.d/* > ~/.ssh/config"
If you already have a working Ruby environment, it's not a lot. If you have to start by installing Ruby, then yes, don't bother.
BTW, this does more than "cat", it supports editing and toggling parts of your config (using --include on files that would normally be excluded).
This was my original use case: Switching between setups for remote and office work.
The editing part of "poet" looks good, but it seems like one of those tools that might suffer from being overly developed.