Browser makers are completely removing support for browser plug-ins like Silverlight or Adobe Flash, which were once popular on the Internet. Some older browsers still work, but modern ones do not..
No, one can run A/XE without Silverlight support. But they won't be able to access the user interface except from a browser that still supports Silverlight.
One can still use A/XE on most versions of Windows. Silverlight is needed only on the computer used to manage A/XE. The biggest disadvantage is that it is generally less secure to run older browsers.