Hello @Allison Cunnington,
Welcome to the Microsoft Q&A forum. Thank you for sharing the details regarding the limitation where only one response per user cannot be enforced when submitting forms created with Microsoft Lists. Unlike Microsoft Forms, which provides a built‑in “One response per person” option, this feature is not available in Microsoft Lists Forms. We have conducted several tests to review potential configurations and workarounds. Unfortunately, none of the current Microsoft Lists or SharePoint settings support restricting responses by user or applying custom views solely to specific groups for this purpose. At present, this behavior is by design within SharePoint’s standard capabilities.
I strongly recommend submitting your suggestion through the Microsoft Feedback Portal, which is the official channel where feature requests are reviewed by the product team and considered for future improvements. Sharing your idea there will help bring attention to this functionality and may influence future updates of SharePoint.

If you've already submitted feedback, please share the link here, so not only me, but others can also vote it up.
Once again, thank you very much for sharing your detailed and thoughtful feedback. I truly appreciate you're understanding and patience as Microsoft continues to evolve the platform.
Looking forward to hearing from you!