As someone who's also used and remembered write-rings, etc., this is nonsense. The concern over threats back then was VASTLY lower than today, because the threat was in fact far lesser. Computers were vastly less interconnected and knowledge about exploit tactics was still nascent, and a fair bit harder to come by. Stuff was massively exploitable because in the "good 'ol days" there were a lot fewer computer literate people to think about things like "attack surface", and fewer still who had motive to use such knowledge maliciously. I knew grad students back in the 80's who had written their own illicit versions of "su" to make their lives easier. I.e. local privilege escalation tools. An undergrad banned (and transformed into an overnight pariah amongst his peers) for hacking CS dept servers. All kinds of devices hacked by the curious via some hardware port intended for maintenance or just left behind on the PCB. Those things happened, but the collective impact of much of that is less than one major exploit pattern today (Flash 0-day, legacy consumer routers, take your pick).
No, the root problem vs "yesterday" is just that our computers are cheaper and far more interconnected than ever before. Things like the option-ROM-as-vector being an economically practical technology. Our collective level of ability to ship secure systems is probably far better than it ever has been, but that's almost nothing in the face of an exponential explosion in the pervasiveness of computing. We still ship an incredible amount of insecure software and hardware systems, just because we make so damn much of it. Why design a complex fixed mechanism or circuit for something when you can solve the problem 1000x better with a CPU or DSP? That's great, but "oops, we forgot the security again." Or we didn't, but an exploit was still found and updating is otherwise infeasible.
It seems that ability to ship secure tech needs to be nearly pervasive, enough for a sort of technological herd-immunity (or herd-defense-in-depth), if you will. At this point, I suppose we're looking forward the day when all our little computers are muttering to themselves like trees in a forest chemically signaling about attacking pests.