Plex really is kind of an edge case for me--most of the work (namely, the adding and configuring of suitable storage) needs to be done no matter how you install it, and that's going to be different for every user, so it can't easily be scripted. Installation of the service itself is really pretty easy, whether you use the plugin, the package, or the port. Therefore, IMO, there's less value in this script than in the Unifi one (or the Crashplan one, if Crashplan hadn't turned around and broken the service yet again), or my Nextcloud one--in all of those cases, almost all of the complication is uniform. IOW, with Nextcloud (for example), there are a number of moving parts, but the way they need to be installed and configured is the same for everyone, which makes it ideal for scripting: There are lots of steps, so lots of things for users to get wrong. But the steps are all uniform, so they can all be automated. Saves lots of work, and lots of user error.
Plus I don't know squat about scripting so that's probably coloring my opinion as well.
Everything I know about shell scripting, I learned from Google--but if you look at any of these scripts, the vast majority of what they're doing is simply running one command after another, just as you would by doing it manually. I use a few variables--those are easy enough to handle. I use some if-then logic--not difficult to follow, but syntax matters. Again, Google.