Please inform Netflix that Microsoft discontinued support for their Silverlight product several years ago, and to get their act together with Safari.
Excerpted from Update to the latest version of Safari - Apple Support:
If a website says that Safari is out of date even though you're already using the latest version of macOS or the latest version of iOS or iPadOS, there could be an issue with the website. If you’re sure that you want to use the website, contact the website owner or developer.
Had to switch to Chrome for Netflix. Any ideas?
https://brave.com/
Firefox is a distant second choice. No one needs Google. Installing Google obviates most of the reasons for using a Mac.