What bothers me most about this feature being added is there is no good reason you should need this. A well-written adventure would have inline monster stats right there in the encounter.
What if you write your own?
We run a sandbox campaign with a lot of player driven choices, wilderness, and regional randomness. Instead of a 'well-written adventure' we have a patchwork of adventure hooks, character goals, and re-skinned content lifted in small to large chunks from a huge library of content from all versions of the game.
I think D&D Beyond will be fantastic for our game, especially since one player is on a 2-year sabbatical and Skypes in from places like Bali.
That the current 5e published adventures don't is a sign of atrocious layout and design and a big reason I won't be purchasing any WoTC published adventures probably ever.
I dunno, as a grognard, they're pretty good. Like the rest of 5E - not as tight as Moldvay Basic, or as expansive as 3.X, or as meandering as AD&D, or as mechanically harmonious as 4E - it seems to hit the Venn diagram right in the middle.
Besides, if you don't have to flip to four places in the book to solve a rule dispute, is that really D&D?
If this is so awful, what game is good, then?