Yes, they ridicule, for example, the grapple rules. You know why? Because the grapple rules are ridiculous. There's a difference between criticizing 3E's warts and criticizing 3E as a whole.
Right, but are grapple rules $300/year ridiculous? Even when combined with the other fiddly bits that 4e is improving, do the rules add up to that much of an improvement?
Telling someone who is has never particularly noticed a problem with grappling rules that the grappling rules suck like it should be self-evident is shooting yourself in the foot: 3e grappling rules obviously weren't so horrible that it stopped the edition from becoming successful, so how much value do new grappling rules really add? And if those rules have their own problems (as 4e undoubtedly will)? And if you're trading between playing your favorite half-orc druid character and new grapple rules? Or even if you're just trading $90 for new grapple rules? Really? Especially with the 3e supplements that exist to make grappling easier?
It's a matter of diminishing returns. If 3e is already "good enough," then saying "4e is better!" isn't going to get anyone on board. Sure, New Coke tasted "better" (according to the taste tests). Sure, Vista is a more powerful operating system. But so what? Sure, 4e might have better grappling rules (though, again, that's one of those places where 4e rules might not really be "better" so much as "bad in a different way"). Is it worth giving up what you already have to get?
I'm pretty sure that D&D could re-package the FATAL rulebooks, call it D&D 4e, get some WAR art, and sell like gangbusters (though not everyone would be on board). "Fixing The Other Edition's Problems" is not going to sell D&D to the people who don't have any problems with the other edition, and is more likely to turn them off: "Well, none of these were really problems for me, and I like gnomes, so I guess 4e isn't for me."
By decrying the grapple rules, you alienate those people who had no real problem with the grappling rules. For perhaps a more pointed example, by ejecting gnomes from the PH and claiming "They had no niche!" you alienate all those poeple who found or made or realized a niche for gnomes, but don't have a niche for, say, Eladrin, or Tieflings, in their game. The more this happens, the more things people see that they disagree with (because they LIKED 3e, and continue to enjoy it), the more you've failed to retain those 3e fans.
For my personal experience, I know 3e won me over with the possibilities it offered. I was a 2e player, a big PS fan who invested a lot in the edition, but in 3e, I could be a dwarven paladin, or an elven sorcerer with spontaneous magic, and as a DM I could have my party fight goblin rogues without adding up a laundry list of odd rules and XP additives, and I could have my priest of the God of Fire be equal to any other cleric out there without delving into wierd special powers, and I could be a wizard who learned to use a sword and could train in stealth, and OH THE POSSIBILITIES! Stuff that, to do in 2e, would have required a lot of DM legwork, but that I've always kind of wanted to do.
As a 3e player, a big fan who has invested a lot in the edition, there are decidedly less points of possibility looming in 4e. I could be a...dragonborn warlord? I've never really wanted to do that. And now I can't be a gnome fighter without some sort of special arrangement? And my priest of the God of Fire...I don't know how he's going to stack up against other clerics. As a DM, there's a few more interesting possibilities: more skill-based encounters, longer adventuring days, "boss" monsters, but those aren't totally new and exciting, more refinements of what I was doing already. Which I'm not entirely sure I need, y'know? And I'm not totally sold on the bigger, more mobile combats thing, but even if I was, that's still nothin' NEW.
Oddly, the most exciting thing I've seen about 4e are the
gods. Those seem pretty new and exciting. The monster types also have me intrigued, because I like the granularity of there being a difference between Kobold Boogermasters and Kobold Snotflingers.
Like many people who are satisfied with windows XP or Coke Classic or last year's shoes or blue jeans or the first version of the Star Wars movies, the "improvement" of the next new hot thing is pointless to me at best, and insulting to me at worst. If it can give me something NEW, we might have a deal.