Well, let's look at this from a different angle. What's the pain this is introducing into the game? Either all the players at the table will have themes or all the players won't have themes.
Well, no, they are optional. You don't
have to take one. I have at least one player that would not take a theme unless it specifically fit his character, even if the entire rest of the party had them (although he would probably want to work out a custom theme, but that's a different discussion).
This is across the board. So everyone has a theme. Okay, that's cool. If it's really noticeable in a game, the DM can toss an extra monster in the fight or something.
So your solution for increasing player power for no good reason is to add grind to every combat? No, thanks.
Not to stumble too far off-topic here, but since you brought it up, why backgrounds of all things? It doesn't even save you a feat, since you still only get the same number of trained skills.
It can also give you +2 to any trained skill. I know this is a minor thing, but it's there. You can't just decide it's not there because it doesn't break a campaign to its base components in and of itself.
I don't know who decided "more options = power creep" but I don't buy into it one bit. These are mutually exclusive concepts that only coincide when the people producing the extra options doesn't take into account game balance.
Versatility is
absolutely power, and it's one of the most powerful things you can have. There's a reason CoDzilla exists in 3e--that reason is versatility. If you have one character that can do more things, that character is better and more powerful.
I wouldn't even call themes "power creep" since that term seems to imply the increase in power levels is accidental, while themes are wholly intentional. And, for that matter, wholly optional. If you like the idea of themes but not the execution, you could even just take away from the free scaling encounter and call it a day.
I can definitely see a case for that, but my issue runs deeper. To me, a gladiator isn't a guy that can push another guy 2 squares and slow that guy and his buddies; any character should be able to do that. A gladiator is a guy that can kill you with a broken chair, or kill a tiger using only a helmet, a skirt, and a gladius. Put on a show for the crowd, stuff like that.
And don't get me started on the "Elemental Priest" that is a primal spirit conjurer...
Quite frankly, themes are the best idea WotC have brought to the table since skill powers. Say what you will, but 4e is a much better game now than it was two years ago.
Sure, it's a better game; quite frankly, characters should have had themes before they were released as a game mechanic. I don't need a theme to tell me that my wizard is a disciple of the frost acolytes, nor do I need to be enticed into doing so with a free "gimme" power. I just pick some cold powers and some cold feats and I freeze some punks to the floor.
I'm not going to disagree that themes are power creep
So we are in agreement.
Most of the other theme feature powers seem to be at the level of awesome at-wills; they're often something like 1[W]+ability and a very useful effect. That's a power level I'm quite comfortable with, it's rather like giving every character a version of the Dilettante feature that doesn't actually suck.
You are comfortable with every single character getting a (better) Dilettante? First off, Dilettante is amazing, if you optimize. Second off, if you have to pump up the bad guys to compensate for this new free power, that's just stacking more power creep on top of the existing power creep.
tl;dr Sure I can ignore themes now, but what happens when they go core, and monsters get a power increase across the board?