Just on the contrary, critical applications such as government services or banking could provide a light version that just works, maybe a simple HTML/CSS frontend without heavy frameworks to ensure that the service is deliverable.

Once I faced an issue with the SBB ticket system (Swiss rail tickets) that was not working on my iPhone (maybe 8), not in Safari on macOS, and I needed to buy a ticket on the train as in this particular place there was no offline ticket service.

Such services indeed must have a minimal requirements version.