This isn't always a viable option.
For example, in Sweden, we have stores that are kontantfri (cash-free) and it's projected that almost all of Sweden will be cash-free by 2023[0] to 2025[1]. (Sorry the links are in Swedish but you should be able to use <your chosen provider here> to translate them to your language.)
Given that the nordics tend to trend together, I imagine that Denmark is relatively along the same path to being cash-free, as well.
I think a better (but more complicated) alternative would be to use two different SIMs for separating those apps from an every-day number; however, that comes with the problem of carrying a second phone. Dual-SIM would just present a surface to tie the two numbers together but so would the two phones being in the same area (in proximity of each other) almost all of the time.
In other words, I don't really know how to solve this problem because it depends on everyone else not jumping on the bandwagon; however, to your suggestion, cash will not be a viable option for any purchases - much less, sensitive ones - in the very near future.
[0] - https://computersweden.idg.se/2.2683/1.690197/kontanter-slut...
[1] - https://www.compricer.se/nyheter/artikel/24-mars-2023--da-ar...