>Most cars give you significant warnings that you're about to run out of gas and as a result very few people do.
You will see accident reports where the problem is that the pilot just completely failed to put enough fuel in the airplane and then flew it until it ran out; but that's not the typical thing.
What's much more common is that the pilot takes off with what seems like ample fuel, gets halfway there, discovers weather that is worse than expected, has to fly lower than planned, burns a lot more fuel as a result, discovers that they will have to refuel, can't find an airport with good weather at which to land, and ends up flying a graveyard spiral into a fatal crash caused by disorientation in conditions for which they are not trained.
The majority of accidents are traceable to poor planning or decision-making once airborne; and I tend to agree with the other poster that improved avionics are not going to make a really big difference.
Improved avionics should help with all of those aspects:
1) Continually recalculate fuel remaining upon landing at destination based on ground speed and burn rate. Warn if getting anywhere near reserves.
2) Show nearest filtered airports (those with runways that satisfy both airplane and pilot requirements (max x-wind). If IFR, further filter by approach preferences and if available current wx data against approach minimums.
I agree with you that what you describe is a common accident scenario but imagine a PPL could just hit a single button if they inadvertently enter IMC and the avionics provides a route and vnav profile to make it safely to an airport with low minimums? The most difficult part of flying IFR is that it takes a ridiculous number of button presses on most systems to accomplish that all while trying to also keep the plane straight and level.
I'd be fairly surprised if most (say 75+%) GA airplanes regularly used for purposeful travel lack a moving map GPS and fuel-flow enabled engine monitor. (The moving map is probably well over 90% and it's the engine monitor equipment rate that may drag it down.)
In every airplane I've been in that is equipped with both of those, the pilot has access to both projected* fuel remaining at destination (in minutes and in gallons), has an ability to get a warning if configurable thresholds are violated, and with just the moving map GPS to have a filtered (usually by minimum length, paved vs soft, and sometimes lit vs unlit) and to have the nearest ("NRST") button present a list of airports, distance, and direction with a single button push.
There are things that could be done to make it better, but I wonder if you're imagining a lower/lesser level of equipment in typical GA traveling aircraft than is currently the case. (To the extent that equipment is already installed that provides 90-95% of the proposed functionality, providing that last 5-10% probably isn't going to be the missing piece of the puzzle.)
You will see accident reports where the problem is that the pilot just completely failed to put enough fuel in the airplane and then flew it until it ran out; but that's not the typical thing.
What's much more common is that the pilot takes off with what seems like ample fuel, gets halfway there, discovers weather that is worse than expected, has to fly lower than planned, burns a lot more fuel as a result, discovers that they will have to refuel, can't find an airport with good weather at which to land, and ends up flying a graveyard spiral into a fatal crash caused by disorientation in conditions for which they are not trained.
The majority of accidents are traceable to poor planning or decision-making once airborne; and I tend to agree with the other poster that improved avionics are not going to make a really big difference.