Every signature counts.
If you sign the petition, you show you disagree with the Season 3 finale of The Good Doctor and the fate chosen for Neil Melendez character.
The petition is a way to protest peacefully and is also a powerful way to show that as a viewer, you set against the decision of the producers and writers of the show.
Important fact to remember: petitions are how fans of shows like Lucifer and Sense 8 managed to get what they wanted.
A petition is like the voice of a fandom.