One of the oft-touted "flaws" of 4th Edition is that there are separate rules for creating players and monsters, where 3rd Edition had a more cohesive set of rules that was mostly similar. Of course, prior editions had rules that amounted to basically "make it up yourself", but we'll just ignore that tiny little fact.
In 3rd Edition (Revised) making a monster had you start by picking a creature type, which provided you with a Hit Die. Hit Dice were specific-sided polyhedrals that carried other mechanics with them: an attack bonus, save progression, and skill points. If you wanted to make an undead monster, it had a "poor" attack progression, which meant that for every two Hit Dice it got a +1 to attack rolls. All of its saving throws except for Will sucked, but at least it got to use a d12, right?
From a design standpoint, this meant that to create a huge "beater" type monster you had to really frontload the Hit Dice and/or give it a massive Strength score to compensate for its piss poor attack rolls. As a DM you generally knew your party, and I recall doing this when I was running Age of Worms where I had to strike a very, VERY fine balance between HD and Strength, because if the Strength was too high it could easily kill one player, but if it had too many Hit Dice its hit points would be insane.
Add to the heap that Armor Class was largely whatever-you-wanted-to-use and its a mathematical nightmare, especially when you consider that not all Hit Dice were equal. While undead was particularly crappy, the Hit Dice for a dragon was supreme: +1 to attack per HD, best saves, massive skill points. Having to juggle all these things explains the reason why many monsters had glass jaws or ended up being far too powerful for what their Challenge Rating would suggest.
As a D&D junky, much of the time I had some fun doing this type of stuff. At first. Eventually, the joy waned and it started to get tedious as I starting making more and more original content. NPCs became a chore, and much of the time I just applied a level and class next to their names and committed some basic (and often incorrect) math to the label.
"George the blacksmith? He's probably a level 2 expert, not that anyone is going to attack him, but if they did he probably has +4 to hit with a big-ass hammer and deals 1d8 + 3 damage. Hit points? Feh, I'll wing it when the time comes."
Dont get me started on spellcasting NPCs: I generally panned out the best spells and just told the rest to sod off.
Now monster creation is much more streamlined and focuses more on what you will actually use as opposed to the futile attempt at complete world immersion, which I doubt any RPG has successfully achieved. You pick a role, a level, and then tack on abilities that you want your monster to use and the rest literally writes itself after referencing some formulas in the Dungeon Master's Guide. Its a lot like making a normal character, just without the feats.
What this means is that the end result is essentially the same, just without nearly as many quirks and the road is less convoluted.
Granted, some rules are a bit obscure: I know more than one person has overlooked the little footnote that says something to the effect of "area attacks are -2 to hit", but its not exactly alchemy and after awhile you will probably come to memorize most of the formulas.
On the topic of doling out powers, one poster on the message boards complains that you cannot learn maneuvers that some monsters have. The one that kept cropping up was the bugbear strangler's choke attack. I have to wonder just how many times anyone has bothered to attempt anything like these, even in 3rd Edition where you technically could make the attempt, but it was often more effective to simply make an attack (even at the -4 penalty to inflict nonlethal damage). Even if you did bother to climb up a feat tree to be able to grab someone and start strangling them, I have no idea why you would waste your feats in such a manner seeing as most monsters are stronger, bigger, and have more Hit Dice than you do, which most certainly outweighs any kind of trivial advantage all your shiny feats will grant you.
Its a lot like monks having Improved Grab: sure you ignore the -4 penalty but that doesnt amount to much if the monster has a grapple modifier 10 points higher than yours after the fact.
However, his complaint isn't so much efficacy as transparency, but I think its a matter of him looking at the rules and finding out that nothing there explicitly allows it as opposed to his character not making the attempt when there are many more effective actions to take. 4th Edition has focused on making a much more playable and fun game, a goal that they have succeeded at. Whether the sacrifice was worth it or not depends on your group, but I suspect that Wizards knew what was up while they were making the choice.
That being said, I don't think that 3rd Edition was a system that encouraged you to do whatever you want. There are rules for many things, but not all, and many of the smaller subsystems had so many flaws that its more like the mechanics were just teasing you about things that you could theoretically perform if you didn't mind horribly crippling your character in some fashion and you lived in a perfect world. Things like grappling, buying a castle, or taking ranks in any Craft skill, and on that note...
The Craft/Profession skills in 3rd Edition never did make sense and seemed to exist mostly to justify in a mechanical sense how NPCs can perform their basic functions such as farming or bartending. Few, if anyone, in my games ever bothered with them because we were usually out and about actually adventuring. D&D is an action-adventure role-playing game, not some kind of twiddly "reality simulator".
You can argue role-playing this-and-that, but then you probably dont know what "role-playing" actually means. Players might take ranks in those skills to try and pretend that they are a cut above the other gamers, but in the end if you DM doesnt go out of her way to create situations where you can use those extremely narrow skills then you've just wasted ranks.
In one of the Pathfinder modules it was mentioned that there was a clue that a character with Profession (butcher) could figure out, which sounds creative but isnt when you consider that you cannot make Profession checks untrained and butcher is one of many professions that a character could take. You would have to heavily imply if not outright tell your group that someone should take that for anyone to have it in the first place (thats not even considering what the DC is, as a player might take a handful of ranks in it and be done).
Having rules for those things gave the implication that to have a character that grew up as a farmer that you need to have Profession (farming). To me that just restricts character potential, especially considering how skill DCs worked in 3rd Edition and that most classes got crap for skill points. It was often a toss up between a skill that would be very useful to being able to justify your character's history.