GPS mis-loading errors are easy to detect by using the moving map to zoom right out and display the whole route, before setting off.
A GPS without a moving map is OK for a door stop, nothing else.
Also a good idea to plan the route on VORs or NDBs, and tune in the navaid, for an enroute cross check.
That said, it is much harder to mis-program a GPS than to "mis-program" a VOR. On the latter, setting a track of 180 v 080 etc etc is easily done if in a hurry. In the goode olde days, pilots (including commercial ones) had little idea of where they were most of the time, other than when right on track to/from a navaid. We have an easy life nowadays.
I think basic failures will continue to dominate the avionics reliability picture. For example, in my TB20, most of the connectors around the avionics are high grade mil-spec jobs (the kind of thing you find throughout a King Air) and then they use Vauxhall Viva open plastic crap in the wings, going to the wingtip lights. All one can do with those (legally) is spray some ACF50 in them. A smarter plan would be to replace them with the good ones.
I am getting the whole aircraft corrosion-proofed soon - even though it is hangared.