Is "autoresponder" the only way a user can edit/update their form input?

Moreover, since the "autoresponder" seems to be the only way a user can edit/update their form input, I have to now seek external solutions to allow users to update their data. If my user cannot update the form submission, nothing that does work on Jotform means anything... it becomes useless for what I'm trying to do.

To allow users edit their submissions, there is another option as well. You can place 'edit submission' link to a Thank You page of your form. 

Please review this help article: Setting-up-the-Thank-You-Page