Sorry I wasn't more clear. The online tools were key, true, but also the tables and exposed math for what creatures of each level should have for abilities, HP, attack bonuses, damage for a variety of attacks, and so on. Reskinning is still possible, of course, but I find it more difficult, especially with so few options at higher levels (where our campaign is right now) and without a discussion of the difference between monsters at the same level -- the way there were normal monsters, elites, and solos in 4e. It's clear to me that something along the same line exists in the mosters we have so far, but I find I wish it were a lot clearer what was going on so I could create my own.
For that matter, I'm heartily miss the variety of monsters of the same type. I mean, having an entry on "goblins" give us 5 different types of goblins was awesome -- and there aren't many cases where that exists in the new material yet -- and where it does, it's clear they're doing it in a very 3e way (using character levels) -- which is much more labor intensive for the DM.