I don't quite get the disappointment Was anyone expecting every old monster converted, every 3E feat chain and prestige class redone as a subclass or feat or any ADEU powers version of the classes for people who wanted to play 4e using 5e rules?
Mind you, I think that might be a worthy endeavor, but I wouldn't expect them to give it away for free.
My expectations were low, but I'm not sure even those low expectations were met.
1.) Too much focus on PC conversion, which is the least important kind of conversion. (Adventure/monster conversion is the most important.)
2.) PC conversion is only cursory, e.g. exceptional strength should map to Str 20 not 18, no discussion of dual classing.
The value of an "official" conversion guide has a lot to do with Czege's Principle. Obviously a DM can make things up any time he wants to, but using a module allows the DM to participate in the experience of discovery. Because of this, the "quick conversion" section is actually the most important part of the conversion guide, and for the most part the quick conversion is just a shrug. E.g. it acknowledges that 5E has HP inflation but can't even be bothered to point out that you can get a pretty good conversion to 5E by inflating HP and damage per attack by a factor of about three.
Edit: oh yeah, and
zero discussion of movement rates. That's an egregious oversight because it really is simple: multiple 2nd edition movement by 2.5 and round to nearest 5' to get the 5E speed in feet. MV 9 = 25', MV 12 = 30', MV 15 = 35', MV 18 = 45', Fly 36 = 90', etc.
The quick conversion guide is poor enough that I wouldn't want to use it in play, which is disappointing. When I heard that there would be a conversion guide for AD&D, I expected at
least a table or two for generating monster ability scores like Strength and Dex from AD&D stat blocks.
At this point, it would be false to claim that 5E has any kind of support for running previous-edition adventures in 5E. The doc is actually less useful than my own unfinished guidelines for converting 3E adventures to GURPS: Dungeon Fantasy, which is saying something. Your takeaway should be, "5E is a separate game. Don't even try to re-use monster stats from previous editions. Or if you do, don't use this doc to do it."