The big change in tech occurred at the end of the 80s through the 90s, first with Titanium then Carbon drivers, and the Pro V1 ball. In the 1970s and 1980s driving figures were about 10-20% lower than that as persimmon and small steel-heads were the norm. The stats are out there and clear. The vlogs comparing late 90s and current drives are correct, because by the end of the 90s the Titanium and carbon crown drivers were quite similar to today's with 460cc heads, but in the 80s they were more like 330cc.
No, I don't think 'plenty of people could carry 300yds' back then, because hardly anyone can even do that today. Carrying 300yds means running out to 330-340yds. I could do that with a 7 iron, if I was aiming 100 yds downhill with a tail wind on a bone dry links course, but on the flat in still conditions, no. Not even most top tour Pros can do that today at 100% effort. Big hitters like McIlroy or Ram can carry about 300yds in normal conditions, rolling out to 340yds on the flat, but they are the top 0.0000001% of golfers, not 'most people'. When you see bigger drives than that on tour there is usually an elevation change of favourable the wind conditions, or you are looking at 'long drive competitions', where longer than legal drivers are allowed.
Tour driving statistics are for Par 4 and 5s, where Pros are swinging around 85-90%, which is they max they can do whilst still maintaining control. They are not hitting 'rally balls', which would be more like a 50-60% shot which no one ever does in golf, because you just use a shorter club at 85% if you want a shorter distance, as shorter clubs give you more control. No one ever hits a driver (or 3-wood) at much less than 80%, they would just take a 5-wood or long iron.