It is sad that the latest update break the compatibility with OS X 10.7. My perfectly fine working MacMini can’t be updated because Apple decided of it and now Plex decided to stop the support.
Apple has abandoned 10.7, and arbitrarily decided that some models below a certain point won’t be able to install newer OS X versions. An abandoned OS is not only a security liability for you and the rest of the internet, but software developers depend on libraries and such from the OS maker and if those aren’t getting updated/fixed/improved then it’s a lost cause.
You’re also locked out of newer browsers, newer versions of Flash, and more, all because of dependencies on newer OS X versions.
Your beef is with Apple, not Plex. One of the things you agree to by buying into the Apple cult is that you will replace your computer/device every few years.