Sam,
I can help point you in the right direction to make the email organizer field required.
We have a guide already in place here:
https://theeventscalendar.com/change-required-fields-on-community-event-submission-page/
If you take the first block of coding and copy that to your theme’s function.php it will make the email organizer field required.
You may not want all the fields required in that first array and can remove them as you would like.
If you have any issues please let us know.
Thanks!