I find where it breaks the hardest is the modern players that think the DM using PC style tactics against them is "uncool" or "unfair" or just "bad DM'ing". Just kill those players till they leave your table if your running high level games. If they can do it. It should be fair game for the DM as well.I continued collecting 3.5 books after the edition ended; to date, I'm missing only a couple of the Fantastic Locations supplements, and one or two of the Dragonlance adventures.
Likewise, I'm personally of the opinion that its "downfalls" are overblown, particularly in online discourse which very often analyzes things at a theoretical level without looking at the actual course of play around the table. It's not a simple game by any measure, particularly at the higher levels, but it's not supposed to be. Complaints like "my 20th-level character was completely ruined by one mordenkainen's disjunction" are issues of people not properly engaging with the game far more than they are "evidence" that the system breaks down at that level.
It does require the DM to be knowledgeable about a lot more things than other editions at high level but I do find that if you simply let the bad guys do all the things players can do that players start getting a lot more cautious or die quickly. But that was a problem in 1st and 2nd ed as well. I had players bring me over the years several modules made for High level play. "Isle of the Ape" , "A Paladin in hell" "Castle Gygax" and when the players that had gotten away with high level Hijinxes played in a scenario where everything was geared to kill them they got just as scared and had just as much fun as lower level games. But at some point in any edition monsters just don't cut it anymore. You have to have NPC's with powers, spells and resources that even 15 or 20th level PC's can't wish away or insta kill with their DM special artifact +10 sword of doom. People who think 1e or 2e were any easier to run at high level probably didn't run any high level games. All the problem things are still there, artifacts, relics, teleport, wish, heal, and some of the spells that killed characters and NPC's were save or die not save or suck. I don't know about 4e and I haven't run anything in 5th, only played it, but I suspect if you run them up that high things break and get just as hinky . The one benefit they have is they don't have the years of supplements and books to feed the players imaginations on what to do in between games.
But the bottom line is if your mage can make a simalcrum army then every high level mage in your world can do the same thing. Read the Jack Vance short Morreion for a good snapshot of why high level mages probably don't want to mess with each other and how important luck and initiative order are with time stop. (these are the kinds of things you need to be focusing on at high level. The story arc will build itself).
And if you've allowed a High level game in a low magic world. Shame on you. Everything that happens after 8 level or so is on you for letting high level PC's run around in a low magic world.


