A WordPress Multisite feature is wonderful and powerful, but not for most people.
The biggest issue is that it uses ONE database to manage ALL sites. It is more complex to the Admin Dashboard and to the use of various plugins. It also makes migration, later separation, and backups a bit more of a complex issue (wellβ¦. significantly more complex!)
All plugins will not work with multisite. First You check if the plugins are multisite compatible or Not before installing them.
The individual sites cannot add or delete themes and plugins. If they are present on the network, they can be activated and deactivated.
If your site or server is down then it will affect all the sites on the current network.