The singing thing really bugged me as a kid as well.
In some movies I actually did not mind it, as the story was written as a musical so the songs FIT and were just natural progression and flow, you didn't even thing twice about them. After those movies made bank though I guess it became standard to 'if the movie is for kids. Add at least 5 songs into it.' and it just bothered me... because those movies were not written as musicals even though then featured singing. I HATED it when the story felt like it stopped for a character to have a god damn song break. It dragged the movie on and annoyed me, heck it could sometimes be embarrassing when the characters on the screen your watching breaks out into song. Which I know is unreasonable and not really something YOU should be embarrassed about since you're not doing it, but for some reason it was.
Also mentioned 'character deaths to teach kids a hard life lesson' (not including villains, because villain deaths seldom include a life lesson) this... bothered me... not as a theme, but as a way it was treated. If the character was unimportant, had little impact on the story or or just there. It was fine, but if the story treated it as a big thing, had it be important and bring more than just meaning that 'easy sad part' like say 'The Iron Giant' then that story was considered too mature for kids, that kids won't get it, or too dark. All these things added up to 'kids are stupid and will not understand' and of all the things being thrown at me in media as a kid, being treated like I was stupid was the worst and most insulting of them.