Please check out my "State of the Word" presentation from 2016 and 2017, I tried to make the best case I could for why, perhaps once a decade, it is worthwhile to trade backwards compatibility for future relevancy. The reason I have personally not advocated for that trade-off before was that the reward on the other side was not worth it, but with Gutenberg we have a huge opportunity, and incredible user demand demonstrated by the adoption of the beta plugin, that I think makes it #worthit.