You'd hope they do but many are not implementable in a quick manner or to the scale we have achieved with space based services. The question was about if they all failed at once, which is why we are quite concerned about coronal mass ejection and other space weather that could knock out our space systems all at once.

There are ground based PNT/augmentation seeking to lessen reliance on GNSS/space based PNT.

The US considers some of these capabilities as critical infrastructure with limited alternatives. Some are unique like the ISS and Hubble.

Remarkably GNSS is one of the largest components of the space industry. Near everything has gps or timing requirements now. https://brycetech.com/reports/report-documents/Bryce_2019_Global_Space_Economy.png