Fail, on so many levels. Some monsters will use magical treasure, others might not depending on the intelligence of the monster or other factors such as whether the monster is actually aware of what it has.
Treasure should be listed where it is actually located. Those 500gp gems and the periapt of wound closure are inside the stomach of the purple worm. If the party doesn't search there then they will not find the treasure.
Listing everything in one place like some prize package awarded on another exciting edition of, You Beat the Monster, seems cheesy.
In the delve format each monster's equipment is listed at the bottom of their statblock. Any powers or abilities granted to them by magic items is factored in.
So yes, in 4e monsters do make use of magic items.
Listing all the treasure in in one place doesn't mean that the PCs automatically find it. That list tells the DM where it is and make use of that information as they see fit.
My gut tells me that most of the objections to the format have to do with the implementation, rather than the core concept. Improve that, and you can probably get the best of both worlds.
I think another objection is that the format is meant for people who run the adventure and not for people who use adventures for ideas or convert them.
For example, if you're not playing 4e, having all the 4e stat block in one place isn't any help you. The old format where there was a master map and a key with a description of all the rooms is much better for converting because all the information the converter needs is in one place and identifying any information that isn't useful is easy to skip over.
By contrast, a converter would need to wade through each two page spread for every room, rooms, or whatnot that have monsters in them to find the few bits of information they might want.
That said, if you do run 4e and are playing the adventure "as is" then I agree with you, it's implementation. Wizards still has master maps and keys, but I think that if they fleshed them out more, then they could address some of the problems people have with it.