Too many to recall, but will try to list some at least:
My Hero Academia: I had a similar problem with Nolan's Dark Knight. It's hard to take superheroes so seriously. Seems too childish.
Before Green Gables: Prequel to my top1, authored by a different, more modern writer and director. A simple, kid-friendly story as opposed to the deep and more family oriented original, that had a larger than life agenda to convey.
Irresponsible Captain Tylor: Too goofy for me.
A Little Princess Sara: Another childish instead of a family oriented show. Discussing grave matters in such a naive way.
Boys Over Flowers: Girls oriented. I prefer a more realistic style as well.
Starship Operators: Don't remember exactly, but was plain boring in general.
Wellber no Monogatari: Sisters of Wellber: Little fairy-like creatures with their over the top reactions don't strike me as interesting to begin with.
Seishun Anime Zenshuu: Not enough of the stories are actually any good.
Your lie in April: Another predictable and naive anime like any other. Too unoriginal.