Mark...I almost agree, with one exception. I agree that the broad topics are almost too easy for folks to enter anything they want from that park - as you said, just posting their favorite Disney photo. However, the spirit of the theme as I see it would be that the photo should be both on-topic, and the best possible translation of the theme. In the voting, for example, there might have been a few photos that I thought were excellent photos, but to me didn't impart the feeling of 'Animal Kingdom'...they may have had the technical excellence I look for, the creativity I look for, but in voting I try to weigh all of those elements including how well the theme was conveyed in the shot.
Of course, it's a whole other argument as to whether the majority of the voters use a similar system, or vote based on an entirely different standard - anything from scenes they like visually to favorite locations or subjects to being friends with the person that took the photo to voting for anything with a cute kid in it! And being a non-competitive challenge, in a generally friendly and non-wagering style, I can accept whatever standard folks feel like using and just feel honored to have an entry of mine make it to the final round.
So...I guess I do agree with you - the broad topics are too easy to enter, and therefore get tons of entries...and with such diverse entries, maybe they are harder to vote on since there are so many great photos in such a myriad of styles and subjects. And I'd like to see slightly narrower topics too. But I would hope at least some voters try to think on the adherence to and conveyance of the theme when voting, and if not, then I take the C'est la vie attitude!