This plugin has all the functionality you'd ever want from a form builder and more.
However, form handling is not included in the "Free Version", which means you can't use the plugin unless you pay for it. This is totally fine if the plugin was promoted as "Premium Plugin", but offering a "Free Version" which cannot be used in any working environment whatsoever is just ... fishing.
Free Versions should do what the plugin is meant to do, while saving the extra functionality for users who pay more (that's the concept of Free vs Paid version).
Just add a submit button to the forms and let developers code the form handling (no one is asking you to with a free version).
Wondering how it's getting 4+ stars with the WordPress community (which usually encourages open source, or at least a working free version).