YouTube now provides nearly all their videos in HTML5 or other non-Flash format, so you can run YT on iPads and iPhones and other devices that don't support Flash. YouTube is not a problem.
There's no direct substitute for Flash for things like games that were written in Flash.
Microsoft developed SilverLight as a "Flash killer" some years ago; it had about as much success killing Flash as their Zune did at killing the iPod. SL is still available but nothing is written in it and MS is desupporting it.
It's important to note that the Windows 10 browser "Edge" does not support plugins at all. This is a clue. Plugins are a security risk even at the best of times, and they load down the browser.
The future is without plugins, at least of that old sort.
So I can uninstall Silverlite also, with no repercussions?