Hellow Mr. Gordon.
On a very severe high speed accident, when comparing a modern 2500-3,000 lb modern car (any modern car) and a volvo 122, I think we are much better off on the older volvo (assuming you are wearing seatbelts, without seatbelts the modern airbags can be critical). Modern car safety engineering has many compromises in it, including cost of production (I doubt they have 5,000 welds in it for example). Remember, at the end of the day, they need to make a profit, and they need do compete with Hyundais built with much lower labor cost. Also, these modern high strength steels are not necessarily better in absorbing energy. Their yeild strength is higher, but their ductility is lower (i.e., once they start bending, they offer less resistance) and of course, they cannot be repaired. Modern steels are good for meeting the normal suspension loads with much less metal (i.e., save money). In the case of the 122 structural design, there were fewer compromises. For example, pedestrian survivability, or survivability of a much smaller car that collided with you was not an issue. Profit margin was not as critical, because Volvo, through its reputation and keeping the same body style for 14 years, could afford the extra cost of building the car stronger, and of course there were no Asian competitors (Japan was still trying to catch up back then, and there was no Korea or China).
Comfort: Yes, there has been progress in this aspect. Creature comforts that you could only find in luxury cars in the 60's, are now in all cars. For highway trips, I have an airconditioned 1968 Imperial (7.2 l, 12.5 mpg, with old technology, you can't have everything in one car!).
Times have changed, no question. And they have changed for the better, on average. Even though the 122 or P1800 are superior in many of the most critical respects to the modern cars, they only built 600,000's 122's in 14 years of production, and I am guessing 200,000 P1800's. Honda makes that many cars in probably a week! So, a lot more people nowadays have access to cars, and their pollution is much reduced. They are also safer, for the average driver (i.e., ABS, traction control etc are great for the general public, but if you know what you are doing, you don't really need it).
This progress however, has brought degredation in other aspects (and to be fair with modern cars, we compare them with the volvo's which were the best in their class, there was a lot of junk built back then). All this complexity means that maintenance and repairs are far more difficult. Try replacing an alternator on a modern FWD car. So, it is natural, that when the components get old and the frequency of failures start increasing, it is uneconomical to maintain it. The engines themselves are much more complex, more difficult to rebuild, and the overall design is more biassed towards cost reduction rather than durability or rebuildability (you will be shocked if you knew how little money a modern engine costs to the OEM). In therms of engines, you will often see an aluminum head on an iron block. As you know, that combination tolerates very little overheating. I have overheated B18s and Chrysler 440's with no damage many times to a point that a modern engine would have failed. Another example is BMW engines with aluminum blocks have a Nikasel coating of about 0.001" thick (once that goes, the bore wear is very accelerated). I saw on a shop mannual that volvo bore does not have to be machined/rehonned even when bore wear is 0.005" deep (0.010 on diamter). Another good example is replacing ball joints in our old volvos. It can be done in 30 minutes, without even removing the control arm. Try doing that in a modern car. Another example is the front dual wishbone suspension on our volvos. Most cars of this price range will have McPherson struts (much cheaper, but don't work as well, and not as durable). The list goes on and on. And let's talk about crush worthiness. It seems to be that the modern cars are design so they cannot be repaired after an accident, so that you will have to buy another one. So, all these respects, moderns are disposable, by design.
The trully substantial improvements in automotive engineering took place in lubricants and tires, which we can take advantage with the older cars too.
So, in summary, the modern cars are, on average, better for the general public. But for the well informed enthusiast, a modern car cannot give you the driving pleasure combined with such low cost (low due to low initial cost and/or holding on to the car indefinately). When we talk about driving pleasure, please do not compare a 200 hp modern volvo with a 122 (there can be certain types of roads actually when the 122 will still be more fun to drive than a modern 200 hp volvo). The comparison will have to be betweem a 100 hp modern to a volvo 122, or a 200 hp modern to a 200 hp 60's car (i.e., Jaguar Mk II or Porche 911 or a highily modified 122/P1800 ...).