Pre-modern climbers were likely much worse, for a variety of factors. First of all, in agrarian societies only a small segment of the population (mostly nobles)

Pre-modern climbers were likely much worse, for a variety of factors. First of all, in agrarian societies only a small segment of the population (mostly nobles) had any significant amounts of free time to pursue activities unrelated to food production. So the population of climbers was much smaller. On top of that, nutrition in general was a lot worse. Most of the population lived on diets just enough to survive. And lastly, literacy and information transfer was highly limited so climbers would not be able to teach each other their techniques as effectively and couldn't google the best climbing places.