Some rose tinted spectacles there I think.
Modern cars still breakdown but the failures tend to be either electrical or major mechanical ones, neither of which are fixable at the roadside. The AA, RAC, Greenflag, National Breakdown etc are just as busy as they always were, and that doesn't include the smaller more recent providers.
Anyone who has worked for manufacturer's warranty providers will tell you that they're busy too; the company I worked for had at least five people on the road, and meeting colleagues at main dealers happened every week. We were at Maidstone Mercedes so often that they told us to just unload cars without checking in first!
You could proably convince me that cars designed in the 90s and 00s were better than ones from 20 years earlier, but the increased complexityand cost of getting work done means that we've gone backwards; for instanc3 the cost ofa replacement clutch can easily kill a £1000 everyday car
You may well be right there
However, I am sure that what I saw with my own eyes and heard within the (adult) driving community around me at the time, then my own experience on the road from the late 1960's, that the type of breakdown was usually more serious with serious engine failures. Maybe the TYPE of breakdown we are now talking about has changed? Here is a Which list of the 10 ten most common breakdowns, which importantly is echoed by the likes of the AA.
https://www.which.co.uk/news/2011/08/top-10-reasons-for-car-breakdowns-263068/https://www.theaa.com/breakdown-cover/advice/top-ten-breakdown-causesI suspect, from what you say Nick, that the complexities of modern cars, with all their electronic wizardry, has made all the difference from a reliability point of view, in the positive (carburetors, distributors, capacitors, points, etc have all gone), bujt the systems themselves can have "computer" troubles.
It is an interesting subject, but either way I still love with nostalgic eyes those big, heavy, British, cars of the 1950's into 60's.