I've played MGS4 several times through, and I just went through MGS1-3 in the past month, and I'm not sure what you're talking about. Most specifically confusing to me is the bolded part. Besides some of the survival stuff from MGS3, what can't you do in MGS4 that you could in the others?
Confused about it all or just the point about the controls?
MGS4 streamlines a lot of the first person stuff that was introduced with MGS2/3: leaning, tip toeing, pulling yourself up to take a look when hanging off ledges etc. Also, interaction with the environment is reduced, not just in terms of the Survival aspects from 3 either. You don't get options like shooting fire extinguishers, steam pipes, etc. Lockers, bins and other things to hide in are completely negated by the (admittedly awesome) Octocamo. So while the controls
are much smoother and the camera way better, I found the encounter options to be reduced. They may not seem like much, but Metal Gear is, above all else, about the details.
Then, to top it off, the game itself doesn't meet your new abilities. It is still designed like an old Metal Gear game and the new controls make most encounters a joke. There is no threat when you're caught, no real need for stealth. The AI can't match you, the level design is still harking back to the 90 degree angles of MGS2 when you can hide literally anywhere. At least TPP embraces non-stealthy encounters and matches your new capabilities with large, adaptive, scalable and coordinated teams hunting you down.
The biggest crime for me though, is that gameplay mechanics are simply discarded as the game goes on. Where is the hiding on the battlefield post Act 2? How is that stretched, pushed or subverted? What about the tailing section post-Act 3? We get half an Act dedicated to a gimmick, whereas previous Metal Gears would have a five minute section for it, have a decent in-game reason for you to do it that didn't feel contrived, and they would challenge your understanding of the new mechanic as you went on (great example of the latter is the High Frequency Blade in MGS2: starting with one room of Tengu, then a room full of Tengu with less cover, and finally culminating in a badass showdown with Solidus). We hardly get any time with either of these things before we're on to the next level which is straight Metal Gear stealth again. The Rex vs Ray fight is a great gimmick, but it is just that: a gimmick. It lacks any gameplay substance, something indicative of the game as a whole IMO.
Don't get me wrong, I played the shit out of it. My opinion comes from many hours of experience with the entire series.
Personally speaking, I found MGS4 waaaaay too easy compared to other Metal Gear games. The game just throws way too many weapons at you early on, making it really easy if you're discovered to go Rambo on their ass and the Octocamo makes the stealth aspect too easy as well. Enemy AI isn't anything to write home about either and because the areas are so wide and open it's really easy to escape enemies unlike in previous MGS games, where you're put into tight environments with a few hiding spots to run to.
I also didn't enjoy the Boss battles anywhere near as much as prior Metal Gear titles and a lot of them just relied on the same tactics - shoot to kill "Beasts", turn into "Beauty" and kill them each and every one having the same attack pattern (which became really repetitive by the time you got to Screaming Mantis), rinse, repeat. The Vamp fight was forgettable, the Rex vs Ray fight being the only interesting new encounter but still felt like that betrayal for Solid Snake to be piloting a Metal Gear considering how much he hates them and the Liquid Ocelot fight is not good on replays, just relies too much on nostalgia and the mechanics of that fight are clunky as hell. And the CODEC is cut back ten fold too, which was a large part of the Metal Gear experience to me.
I've got to agree with him, MGS4 just doesn't satisfy me in the gameplay category at all. I prefer MG2, MGS1, MGS2, MGS3, Peace Walker, Ground Zeroes, MGSV and all of the non-canon spin offs to MGS4. The only game weaker is MG1.
This guy covers pretty much everything else wrong with this game. Man, if I weren't already married....