I don't think you were tricked to begin with. The movie isn't supposed to move you or impress you in the same way as something like Lord of the Rings or Studio Ghibli productions would. It was merely an extension of the series, and as such, builds upon the series' characteristics: whatever is present in the series, strength or weakness, will be amplified in the movie format. This is almost to be expected from K-On!, given that it was never intended to have a strong story. Granted, other movies have a different approach, but that is neither here nor there.
I shouldn't have to point out that it is quite disrespectful (rude, even) to dismiss something by challenging its relevance. It matters because your review was in great detail, showing that you cared enough to discuss it. I am not criticising the validity of your opinion, nor am I commenting on your review, which reasonably justifies your thoughts on the movie.
Instead, my main concern lies within the consistency of the numerical scores you gave the movie. I find that a score of 3/10 contradicts your review and assessment (you gave the movie 2/10 in the poll): whereas your review makes it clear that you wouldn't recommend the movie, a score of 3/10 or 2/10 implies that there are some redeeming values (consider that AnimeSuki gives it as "bad" and "very bad", respectively, not "painful"). If there are no redeeming values, it would have been more reasonable to assess a score of 1. Again, I am curious to know where that 3 and 2 come from, and it would be polite to respond
From a personal standpoint, I
never give numerical values because that requires objectivity in the form of a standardised system. This is, naturally, an unwise use of my time: instead, I assess shows based on whether they work for me or not.