> I decided that my system would stick with .160 - since I have a frontend that does > everything I want, and the new built-in interface for Mame is pretty poor for 2016
You are aware that you never have to interact with the new built-in interface if you don't specifically go for it, right? Launching games from the command line or an external FE works exactly like it did beforehand, and you never see the new interface.
Of course, if everyone decides the new interface is bad and never files any bugs or feature requests on it, then it will never meet their needs. MAMEdev did this as a friendly gesture to users; we now need users to reciprocate.