Am no expert in this area, yet your post to the community deserves some response.
I understand attempts to set up medication reminders for your aging Dad aren't working as they don't sound:
You may want to reach out to Apple's Accessibility Support Team [Link below} at the bottom}
or to look for a solution in Apple's online articles, or user-guide (suggested links below).
You may have settings in place that stop or reduce the movement of some screen elements,
could something there e limiting the alarm? Stop or reduce onscreen motion on iPhone - Apple Support
Else: You can add other Apple apps to Assistive Access in their original form:
Add, remove, and customize apps for Assistive Access on iPhone - Apple Support
Also: Set up Assistive Access with other accessibility features for iPhone - Apple Support
Eg: says:
"Assistive Access works with many additional accessibility features that support vision, hearing, speech, and physical and motor needs. To learn how to set up and use other accessibility features, see Get started with accessibility features in the iPhone User Guide.
For more resources, visit the Apple Accessibility Support website."
There are lots more "how to" support articles available in the Assistive Access User Guide - Apple Support
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More support if needed:
You may want to contact Apple's Accessibility Support Team:
How to contact Apple for help with accessibility features - Apple Support
or
Apple's Accessibility Support Website
(NB: You can "Get Support" from the link at the bottom of their website:)
Accessibility Support - Official Apple Support
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If you wish, you can provide feedback :To provide feedback about an accessibility feature on an Apple product, you can email the Accessibility team: accessibility@apple.com.