The iPhone lets you change the default text size, so you can fit more text onscreen or see larger text more easily

To change it, open Settings and scroll down to Display & Brightness > Text Size

Slide to the left to decrease the text size and see more items on screen

Slide right, and the text will be easier to see

The text size in compatible apps will also increase or decrease as you change the system size

Even larger text sizes are available if you turn on Settings > General > Accessibility > Large Text

This will let you make the text significantly larger