Which is why powers are good. If you're limited in your scope, say a new player not sure what your character can do, powers give you ideas of all the cool stuff possible. Likewise if you're a new DM who isn't comfortable adjudicating ad-lib then the players still have interesting things to do.
This I'll absolutely grant from the DM side. I've had too many new players trying to do cool stuff to grant it from the player side, though.
But, as I'm capable of making battles interesting (assuming I'm not likewise bogged down with inertia), powers just get in the way. I'll touch on why after the second quote.
For what it's worth, this isn't just a 4e problem. I'm not going to pretend 3rd and Pathfinder aren't stifling in their own ways. If a player wants to do something that's supposed to require a feat or skill or class ability, that's just awkward. I usually let them go for it, but then why do we have all these restrictions and powers in the first place?
This is where you lose me. If a character is too focused on his sheet, what makes you think they'll be any more creative otherwise? Removing options in general won't make anyone more creative the creative types are still the creative types, those that aren't still aren't. It puts a greater burden on all players and DMs. In a perfect world every gamer is creative and every DM is great, but that's just not reality.
In practice, I think that effects creativity because I've seen creative players stop innovating when presented with large numbers of pre-defined options. Theory tends to back that up. Humans only process through a very limited number of options at a time (analysis paralysis, etc.).
Now, if I'm having a tactical minis combat (be it OD&D, Warhammer, 3.0, Pathfinder, 4e, whatever), I want the focus to be on the map. I want everyone looking at the map for options. If they can't find them, that happens, but people will be more creative when they're hungry for more options than if they're already full to the gills.
In my experience, every player being creative is closer to reality than not. I'm picky about my players, but even the rejects wanted to play because they're getting something out of roleplaying that they can't get out of computer games, books, or movies.
There are other reasons to play, but being able to express creativity outside the bounds provided by a computer game, book, or movie are a big part of it. Granted, that creativity isn't always focused on combat, but even players I won't let in my game tend to be rather creative people.
Now I've also seen, disastrously as it turns out, that leaving a purely blank slate results in people seizing up. So I'm not suggesting 5e be a narrativist free-for-all, but a one page character sheet that says "if you can't come up with something creative to do, stab the nearest enemy in the face" is all a lot of my players need.
Cheers!
Kinak