But they have the advantage of being "core assumptions" and not latter added variant rules. If a system is build from the core up with certain design elements, it will usually be better at it then just some variant rules. And as such I say it is a valid critique to say that a certain system starts with different assumptions then you prefer.
And thus I think it's not a misconception that 3.5 is lacking in certain regards, even if there are variant rules...
Again you assume everyone looks at all of these as problems, which I find hard to believe since we aren't a hive mind (You know, like how not everyone looked at the Wizard as a "problem"), as well as that they like all of them meshed together. Those are pretty big assumptions. I know I like some of them, but I don't like the way all of them came together in 4e and the effect it had on the feel and play style of the game for my group, so for me 4e is not a better choice. YMMV, and all that of course.
The actual misconception is again that 3.5 never addressed these problems and contrary to your popular belief I have seen posters make those type of statements. You don't believe that out of all the people on this board maybe a few or even some have never seen the rules in UA? Well I find it just as hard, especially after I brought them up and people did act like they had never read them before, that everyone
does know about them. Neither one of us can prove this and since my thread doesn't in any way impede on your fun with 4e...why do you care?
The biggest issue with variant rules is the lack of ongoing support. How much do you want to have to adapt every further supplement to fit it to your variant rules. If you add reserve points, characters can fight longer. An adventure that based a lot of its pace and difficulty on attrition will feel different (probably a lot easier) with an extra pool of hit points between combats. (Though to be fair, it probably won't affect the typical 3E Adventure Path

). If you switch to the 3 base classes (Expert, Warrior, Adept?), what do you do with NPCs in adventure modules or new PrCs and Core Classes? How do you integrate these concepts?
Sure, you can always convert the individual class or NPC if you think you want it. But it introduces more work. And you didn't really wanted more work. You wanted to follow a different assumption.
Buying 3 new core rulebooks and then maybe getting the supplements is far easier. Because you just need to browse the books and pick the things you want - they work "out of the box".
(I might also argue that some changes are easier to do in 4E then in 3E - the rules are more transparent in may ways. It's a shame that it's not OGL, really... Try removing magical items in 3E and try removing then in 4E!)
The funny thing is the fact that most of these things are labeled as "problems" means they are probably already accounted for in the rules but the core rules handles it badly. Taking your example of reserve points...so what, people have been complaining they want their PC's to go longer without having to rest... this solves that problem, so why would they run into a problem of adapting anything... a game sessions would probably get more done, but I don't see how this causes any problems...since that's what you wanted. Reserve points double hit points, so expect your PC's to go through, on average, 2x as many encounters before having to rest. Just doesn't seem that hard to account for, and after a few play sessions you'll probably have it down pretty much to a science.
Buying 3 new corebooks and the supplements is only easier if...
A. You like all the changes they made
B. Don't care about the investment you've put into 3e
C. Are ready to ride the supplement train again, but of course there''s no guarantee new problems won't pop up and need to be fixed with...variant or optional rules (Skill Challenges)
D. Actaully like the new game enough overall to invest in it.
And I would argue that regardless of how easy the changes are to make in 4e, if you don't like the underlying basis of the game you probably aren't interested in using it. Why is it so hard to believe that many here would rather continue their play experience with 3.5 and tweak it, than pay to switch their play experience totally over to the assumptions of 4e and then still have to tweak it?