In practice if they do not make it easy to pay then I just park without paying. The 1/10 times I actually get a fine works out to be cheaper than paying for parking up front.
That said, roadside parking is far more hit and miss for ticketing, but as a source of revenue, most councils take it fairly seriously here for the free money.
And if you don't pay hundreds of pounds for a smartphone, you are not allowed to park? Or if your battery is dead? Or if your religion prohibits the use of smartphones?
If true, I bet framing it that way to the public would help get people on board with some law reform.
No one should be depending on Google or Apple at a government or city or educational level in any way, including in the US.
You can usually also find which car parks have spaces with the apps, to save driving around. It is possible to go cash only still - but it is a pain.