1) Why are the wizards require to basically play a resource management game that no one else has to?
2) What party in 3E travels when their spellcasters are out of spells unless they absolutely have to?
3) Why does every solution you present to spellcasters being more powerful than nonspellcasters in 3E involve weakening the spellcasters?
4) 4E does niche protection much better than 3E. Each class has an explicit role and a lot of tactics and abilities require teamwork - the leader heals and buffs the defender who marks and sets up a flank so the striker can flank and attack while the controller keeps the rest of the bad guys under control. In my experience running 30+ games of 4E, every player does get a chance to shine individually during the same fight.
5) Tom and Mike lock down tough enemies with marks, preventing them from fleeing or moving. Cassius the warlord takes care of any problems the fighters can't while Dan and Cody blast the enemies and control the battlefield with their tactics. It requires teamwork and individual specialization in order for them to win a fight.
I have numbered your points to make it clearer which I am addressing.
1) So now everyone has to play a resource management game? I don't see how that is an improvement.
2) Mine. Continuously. Because the party wasn't based around the spellcaster, but around the story. If the spellcaster always gets to burn through whatever spells they want as fast as they can, and the rest of the party just has to deal with it, then yeah, it isn't going to be much fun. If you want to teach your spellcaster to hold on to one of those fireballs, have the next encounter be one in which his wasting of the spell previously wasn't needed and now it would have been really beneficial. You can condition your players to play the game to the story, not to just the rules, provided the rules are flexible enough.
3) I don't feel that I am saying to weaken the spellcaster. I'm saying just because a car can go 200mph doesn't mean it should. I'm not advocating giving it a smaller engine, but instead educating the driver to follow the speed limit. And when they speed, give them a ticket.
4) Oh, don't get me wrong, 4E does benefit from the roles it gives, but you can have success with a party made of all one type as well. If you play the roles tactically, it requires everyone. But it isn't as rewarding in my opinion. I don't however see how they get a chance to shine. Maybe for one action, but anyone can do that with a crit. I haven't played 30 sessions yet, maybe only about 20+, but I have found that there are still powerclasses, and that they aren't as interesting as in 3E.
5) Enemies aren't locked down with marks. They suffer some negative effects for being marked, such as suffering Opportunity Attacks and penalties to hit, but with the discrepancies in AC/Def, the -2 is negligible. The healing is the primary role of the leader, but any class can take a feat to gain abilities from another class, which just means you wait for them to be able to use that ability again (like waiting for the wizard to rest). It requires teamwork and tactics to win the fight, but it doesn't take specialization. Specialization is a method, but not the only one. I won't even say it is the most effective one.
I can come up with as many examples of how 4E is broken as I can about how 3E is broken, but I prefer the way 3E is broken to the way 4E is broken. To go back to my driving/car analogy, now everyone has a porche. And it can only go 60mph. You might have different tires, and yours might be red, and mine blue, but the engine is the same and the brakes suck. And still no cup holder.