It's a fair point, but by this rationale no new DBs or PLs should be made. Most of these die off or become niche, the ones that really become fundamental are few and far between. This idea that we have to drop everything and go "learn" this new thing is bogus. Folks in tech often seem to buy into the hype of some new technology all too easily, riding the wave of excitement. So their shouldn't be any concerns, of "yet another editor”.

BTW, I'm not saying this won't be successful! It looks interesting and I am excited, GitHub does great work, but you keep it in perspective.