Having been on the other side of a messy ruby project, which had large parts of itself overridden by some addon scripts, maybe that's a good thing!
As always, engage your brain before doing anything and you don't need to use these features, but it gives you the tools to do "smart things" that Go simply can't. This, among other things, means that Jekyll will scale reasonably well with your website as your needs grow, without having to add features to Jekyll core, using your own fork of Jekyll, or switching to something completely different.
For example, I have a little plugin[1] to work around a bug[2] and to skip the hard-coded requirement to have a date in the filename.[3] Is this ugly? Yes. Is this fine to generate a relatively simple personal website? Also yes.
[1]: https://github.com/arp242/arp242.net/blob/master/_plugins/no...