It seems to me that text font sizes for town names in maps have reduced in recent years (nothing to do with my eyes deteriorating 
). On my iPad I eventually found a way to make text larger:
Settings/Accessibility/Per-app Settings/Add App/Maps/Larger text/On
Thought this might be useful posted here.
I use the same for Maps on my iPhone. My eyes are certainly getting worse, but Maps and Messages really pushed me over the edge.
There’s a Control Center widget for text size (the icon displays two As). When you invoke it, there’s a selector at the bottom allowing you to choose to change text size only for the app you’re presently in vs. globally for all apps. Good stuff. 