It's planned obsolescence. That's no surprise from Apple, the people who brought us iPod touch with a un-replaceable batteries, macbooks with soldered in RAM, and 17 steps using 2 specialized tools to change battery in iPhone 5 etc.
The new OS looks like crap on your old (non-"retina") hardware that is otherwise still working fine. Sounds like time to drop another $1500 for the latest macbook. Super for Apple and their stockholders, sucks for you. I'm liking my Lenvo T-series laptops running Linux better and better every day.