I had a 67 Beetle as my first car and I distinctly recall its top speed being over 70 mph, maybe around 72 or so. Freeway speed limits at the time were 70 and I generally had no difficulty staying reasonably in sync with traffic (except going uphill!). I wonder if the newer ones were hampered by emissions stuff or different gear ratios.
Memories can become distorted over time but I seem to recall my Beetle being pretty darned reliable. In fact Beetles were renowned for quality of construction compared to some of the domestic crap that was being produced at the time. Comparing them with modern cars isn’t really a fair comparison.
One of the issues with air cooling, exacerbated by the fact that the engine was so small to begin with, was the difficulty of producing enough cabin heat in winter in northern climes. For that reason, Beetles had an optional accessory called a gas heater which was literally a gadget that burned gasoline to produce heat. If that sounds unsafe, it probably was, though probably no more so than the fact that in a front-end collision the only thing between you and whatever you hit was a gas tank! Hey, we were Baby Boomers – we lived on the edge!