1.8.8 seems to be broken for me. OS 10.9.5/MacbookPro 13.3" from 2012 (i.e. no touch bar)
Symptoms : IDE starts up, loads boards etc, opens window to default sketch and immediately quit.
Looks like added touch bar support broke IDE for older Macs without touch bar; (reverting to 1.8.7 resolved the problem)
I think you diagnosed the problem correctly. The Arduino developers have already been notified of this bug and have made a fix:
If you want to try it out, you can install the Arduino IDE hourly build:
The hourly build is primarily intended for beta testing and may not be as stable as the production releases. However, the fix of this bug is only one of two significant changes made to the IDE's code since the 1.8.8 release so I think it should be just as good as 1.8.8, except without the touch bar bug.