Was this tight rostering you mention, really as commonplace in the 1980s as it is now? Somehow I doubt it, after all society has been cost cutting for decades since then so I suspect it's more common now than it used to be, as part of this over-optimistic planning that often fails to allow for a lot of realities. I commuted to school during the early 1970s, when there was enough rolling stock and staff around that late trains were often substituted by additional services, but yes, I fully acknowledge that those days are gone.
But gone for ever? Maybe this shouldn't be the case, maybe we just need a Government with the courage to invest more heavily in rail travel, for both passengers and freight. Done properly this would need new railways as well as just new staff and rolling stock, and all planned a lot better than our misguided HS2 was. And funded by charging the costs to those who use our horribly over-congested roads.
Now there's a point for me to dispute, I hear you say, many drivers have no choice but to use the roads, so bear with me while I digress a little. Yes of course most drivers will find every excuse going to use their cars, but a great many of them really do have alternatives, they just don't want to use them. Let me start with a discussion I had with a colleague during my working life in transport. I asked her why she chose to drive 3 miles to work knowing the journey was likely to take 30-45 minutes, when it could be done in around 15 minutes on a pushbike. Her answer was that the longer it took, the better, because it was her refuge from work and children, so if it took an hour one morning, that was fabulous because she had a ready made excuse to arrive late for work.
The point is, gone are the days when longer journeys are generally seen as an inconvenience, some people see them as a bonus, and willingly join that congestion, preferring that more congestion is better, and completely disregarding any problems that their personal contribution to congestion causes to others. Or their extra pollution, or accident risk by adding to the frustration of others. If only more people in transport planning realised this, along with many other things that go unnoticed by our "experts".
But railways are different, shorter journey times are still, with good reason, seen as beneficial, and a Government with a proper understanding of road vs rail operations would be pushing to migrate a lot of passenger and freight journeys towards railways.
(Btw, I have a car and I enjoy driving, but I've always used railways, my bicycle and my feet whenever practical, as the thing I enjoy least about driving is congested roads and queuing traffic).
Probably even more common place in many regards - there is a lot more emphasis on walking times & minimum turnaround times now I would argue. In the 1970s there were probably excess coaches (a time of decline) and more capacity and availability on the network and at stations that meant swaps in service were probably easier. But as you've said, you at least acknowledge that times have changed. It's not totally gone no, and swapping around services is still a common part of service disruption where there is availability - this can change on an hourly on daily basis. So one day you might have been able to amend it and reduce delays and another day you can't. The railway is arguably more "efficient" now, but sometimes that means it lives a bit "close to the edge" in terms of spare capacity (stock / crew / network availability) which can cause problems & delays.
You mention "heavy investment" in rail travel, but I seriously doubt that will be happening any time soon - the railway has already had £billions spent on it the past two years just to keep a service running. The government / treasury work in economics and are - in my opinion - inherently short-termist so I doubt that will happen.
For most people time = convenience, and your anecdotal example probably doesn't chime with most people's decision-making processes when weighing up the options between car vs rail.