Why, Novatom, you heartless little cynic!

Perhaps the sad scenes weren't effective to
you, and I will admit, that I, being the masculine, strong-willed person I am, did not shed a tear during the film, but you can't just dismiss them completely. The truth is, Disney is going into some pretty poignant areas that most animated films simply refuse to explore, and they must be applauded for that. The scene where Hiro discovers those Baymax tests Tadashi made before his death was, to put it simply, beautiful. The sentiment was delivered genuinely, I can assure you, and I don't think that most 14-year old children would react as calmly as Hiro did after the death of their older sibling. He only shed one tear on screen, but it made it all the more effective. So... stop griping, little sis, and appreciate that Disney is delving into these emotions.
As for your argument that Frozen is better, I won't even debate with you on that, since you're completely biased already. I myself preferred Big Hero 6 to Frozen. Why? More modern, for one thing. Frozen, for all its grandeur and beauty, trotted basically the same path as Beauty and the Beast, Tangled, and Sleeping Beauty before it. Not to say that it ripped off those story-lines, but that all films had the same sort of medieval, old-fashioned feel. Big Hero 6 was almost dripping with modern technology and ideas, but it still managed to retain its emotion and timelessness. Thus, it's more relevant, and a more original idea for the 21st Century. There are other reasons, too, and I can go into them if you insist, but that's my main point, and not a point that the catchiness of "Let It Go" alone can refute.