Most people have either moved on, accepted the ending, or they just don't care enough to try such a tactic. Achieving anything with a petition is just a pipe dream at this point.
Many people wouldn sign the petition because 'why the hell not?'. You don't need to be hung up on the ending and have moved on and still sign a petition, nowadays it's so easy.
And lastly, you need to stop beeing so pessimistic Atheck, if there's a way to raise awareness or make SP and Kishi understand the situation the ending created then why not use it? If nothing comes out of it you have at least tried