Who in their right mind would charge a subscription fee to download and/or update maps?
Edit: I only found out about this after my father downloaded the app on his phone, and it said he only has 5 downloads remaining before downloading the map for my state. It's extremely dumb for a "privacy focused maps app"
It's not locked, build it yourself or download the apk from fdroid. If that is too complicated for you (or anyone else), maybe pay for the service being provided then?
That just goes with a territory of having an iPhone. When you bought that device you signed on to a culture of consumption that is enforced by the developer of that device.
The developer can't force Apple to let the developer give it to you for free. Apple doesn't tolerate free very well and anything that is free on Apple is likely either a privacy nightmare or is paid for by some subscription you have with Apple.
This isn't a problem with the app It's a problem with the Apple.
If you really want to you can just download them outside the app for free. I like that it provides a free option for those with more time than money and a paid option for those with more money than time.