I use a 23" Cinema Display, and when I'm in the iTunes Store reading the reviews for iPhone apps, the font size is too small to read comfortably.I've explored the various iTunes preferences, but ...

Changing the font size on your Mac can make it easier to read text. You can increase the font size on a Mac in the Displays setting menu in System Preferences.

If you're having difficulty reading the text on your Mac, you can use the macOS Monterey display scaling to make your text appear larger.