I gave up. I recently picked up a 2012 Mac Pro, 6-core Xeon, used for cheap. I installed Yosemite and am running Logic Pro X 10.2.4. Works fine, will have to do for now. I picked up an Alienware R5 17" laptop last year with the six core coffee lake and a GTX 1070 8Gb video card. Lots of horsepower, I run Ableton Live on that on Windows 10, works fine.
There are enough used Macs around for now to keep me going until Apple builds a new computer from scratch. Sounds like they're going to ARM next year? If so, I'll wait until this thread is dead and gone, but I think their plan is to not fix any of this and just scrap all of it with new Apple processors and software. Got a feeling, no proof....
but it sure smells fishy to me.....we have no way of knowing, it could be Intel's fault and Apple is stuck;
I've moved beyond blame, just need something that works and I have it for now..... best of luck.....
if you've got an Apple computer that works, hang on to it.....