Wanted to update my own post with a response I've received from Samsung, so that others searching the Internet with the same problem can get an answer:
"Thank you for contacting Samsung. I understand that you are enquiring about the YouTube app unavailability for your Samsung EH5300 TV model. For EH5300 TV models produced after Jan. 2014, YouTube app has been replaced with LinkToYouTube app. According to Closed Captioning of Internet Protocol-Delivered Video Programming, Samsung has applied IP closed caption to the TV produced from 2014 year and YouTube app has been replaced with a LinkToYouTube app instead.
When you select 'LinkToYoutube' app, Web Browser runs with Youtube website. This is normal operation of the TV and and there is no update at this time. "
So basically, they ran into some problem with YouTube and can't run their app. Additionally, you can't connect YouTube with your TV. In other words, the option to select a video in the browser of your phone, PC, or tablet, and then hit a button and stream it to the TV is also inoperable. That Samsung provides a link to YouTube via browser is irrelevant, as they still advertise YouTube streaming in the marketing for these TV's. False advertising, for sure; buyer beware.
Just bought a Samsung UN50EH5300 and a UN40EH5300. Only one of them has the YouTube app. I tried a smart hub reset on it; no dice. Please advise.