Q: why wont my older ipad update ios beyond 5.1.1?

Because the original iPad is not physically capable of running anything higher.

iOS 5.1.1 is the highest IOS version the original iPad 1 can be upgraded to.

Sorry.

CAnyour get older version of apps that will work on the 5.1.1 iOS like I need an app for Netflix

See if this helps.

Install the latest compatible version of an app on an earlier version of iOS or OS X - Apple Support

Only if the app developer continues to support lower version of iOS.  According to iTunes, Netflx requires iOS 7.0 or higher, so unfortunately, it will not run on your device.