I'm transposing this response from another thread as it has to do with security:
clarkwinkelmann And the same hostings where you can't adjust the amount of web resources are often the same ones that don't allow command line access, which automatically rule them out for any Composer-based package management even if we had a GUI available.
I for one don't want it in the admin gui - forum admins are not server admins. We need security by design.
This is why with email for example the SRS (Sender Rewriting Scheme) allows you to authenticate emails you forward, even though you're not an authorised party and could be spoofing the SRS if you were determined enough to. It's hardly a 100% secure scheme - however the security is in the fact that only the server administrator has the ability to set it up.
In a similar way you don't want forum admins who have a different skill set to a server admin to have the ability to run back-end commands that may break something or may create problems or security vulnerabilities. Also if someone hacks an administrator's account (which is far more likely than hacking the server) then if they have access to running any commend-line back-end commands that's a serious problem for security, even if it is limited to only PHP & Composer. They could discover your database password, and then dump the database and steal it. Note that the MyBB RCE exploit patched in v1.8.30 required administrative access to the forum to exploit and it was graded as a HIGH RISK security vulnerability.
If you ever wish to have the ability to upgrade core or plugins or to install new ones, it should be done through a non-core extension that explicitly installs and upgrades the extensions and does nothing else. If such an extension were to be created it could be bundled with the Softaculous version of Flarum and should be self-uninstallable for those who wish to remove it and use SSH. Furthermore it should create an extra userclass called "Server Admin" and rename regular admins to "Forum Admin" and then that way you can separate which of your Forum Admins can have access to that extension/functionality.
I know that sounds like a lot, but doing it any other way is a bad idea IMHO.