Define “dangerous”. Way more people per year die in motor vehicle accidents than climbing accidents, but of course way, way, way more people go about in cars than attempt to climb mountains. If you compare car deaths per million miles of car travel to mountaineering deaths per million miles of mountaineering, the mountaineers will quite probably still end up on top.
By way of example, in 2020, people in the US travelled a total of 4.9 trillion miles by car. 38,824 people were killed in motor traffic accidents that year. That’s approximately 0.008 deaths per million miles of car travel. If we assume that hiking to the Mt. Everest base camp, while arduous and time-consuming, is not particularly dangerous compared to the actual ascent, then the distance from the Mt. Everest base camp to the summit is approximately 12.75 miles. About 800 people attempt to climb Mt. Everest per year, so that would be a total of somewhat more than 20,000 miles of distance covered. In 2020, nobody died on the climb (there was no climbing at all due to the COVID-19 pandemic), but during the last 5 active climbing seasons, excluding 2020, an average of 7.8 climbers lost their lives, hence, approximately 625 deaths per million miles of Mt. Everest climbing. Therefore, per million miles of travel, climbing Mt. Everest is around 78,000 times more dangerous to one’s life than riding in a car.
Note: This disregards the fact that people normally don’t arrive at the Mt. Everest base camp, go up to the summit and down again, and leave – climbing a mountain like Mt. Everest requires an intricate pattern of acclimatisation, rest at altitude, and familiarisation climbs that extends over weeks – but the order of magnitude doesn’t really change. Even if we assume that mountaineers cover 10 times the distance on the mountain, climbing Mt. Everest is, statistically, still 7,800 times more likely to kill you than travelling in a car. Also note that, as mentioned above, Mt. Everest is considered one of the easier 8,000m+ mountains to climb and it is very popular, which skews the statistics. For example, between 1939 and 2021, 377 people reached the summit of K2 while 91 died in the attempt.