> Even using gear from 30-40 years ago, it is possible to climb with relative safety, the new gear is mainly only an incremental improvement in safety.

Yes, but isn't that also roughly when modern sport climbing started?

Nylon ropes for climbing were introduced about 55y ago, though, I don't know when they became wide spread. Same for modern harness, modern bolts and quick draws. So your ~40y ago might be roughly correct.

Modern sport climbing started, I would argue, around that time. For instance, Red Pointing was popularized in the 70ties [2].

Also interesting is, that Phoenix, the first 7c+, the grade of the route in the Free Solo movie, was climbed in 1977 [3,4] and first free soloed in 2011 (also by Honold).

[1] https://en.wikipedia.org/wiki/Kernmantle_rope [2] https://en.wikipedia.org/wiki/Redpoint_(climbing) [3] https://www.emontana.cz/climbing-milestones-from-6a-to-9c/