Do you find the limited customisation and/or styling of currently existing digital map solutions to be a problem?

Strictly speaking, no. No one customizes anything. They say they want that, but this is a flaw in listening to users. If you watch their behavior, no one (I mean, 1/10th of 1%, at best) customizes.

Now, that isn't to say mapping is good, readable, or often applicable to contexts. Aside from increasing contrast across the board, I can easily imagine contextual changes to maps to make them work better. Let's assume mobile usage now, as that's the key for mapping. When driving, for example (and let's admit people look at their phones to navigate), the map you use sitting at your desk could:
- Get higher contrast
- Get larger labels
- Only label items you need, such as roads you are on, or which intersect the route, not others
- More clearly indicate your position, and the route

It could also do things like automatically turn on traffic status, and turn it off again when sitting and walking around. The user can over-ride these settings, but we know enough about user behaviors in various contexts, and can pretty well sense their context from sensors on the phone that we should give them a better experience, automatically.

I've done a fair number of mapping products, including some user research into this, so would be happy to discuss it further if you have additional questions.