Spoken Content not using voice i selected, even after restarting device?

As a person with learning disabilities in college, I have recently begun experimenting with using Spoken Content to help me pay attention when I read online textbooks and avoid skipping lines, etc. When I select the voice and dialect I'd prefer in Accessibility Settings, the voice I selected is never used on any app or webpage, despite restarting my device multiple times and re-checking my settings. It always uses the default, Samantha (which I have trouble paying attention to because of how unnatural her cadence and intonation are, from my personal experience). Is there anything i can do about this? I have the 'Speak Selection' and 'Speak Screen' toggles on.