I always love how people are "Oh Mojang is so closeminded we will have to ship 2TB of json files for mods blabla" "we'll have to stay on 1.7 forever" "microsoft ruined everything"
The scripted block models are a great idea - they just have to make them more flexible
Also forge will find a way to work around it (until mojang fixes it).
From a mojang pov this was a mostly sane thing to do - they dont have extremely flexible blocks in the game. Pretty sure they thought of how they want to handle more complex things and have something planned for that.
And mods? Well, just stay on 1.7 and switch to 1.9 or whatever when it comes out - or hack in a solution (which forge is probably gonna do)