Given the sheer amount of people going there, I would've thought they had set up multiple routes with different difficulty levels and amenities like carved out paths / stairs, bridges, and tourist shops.

But I was questioning my own assumption there and as it turns out there's "only" a few hundred people a year that try to make it to the summit, with a total of about 12.000 people that did since the 50's. That said, the surrounding national park gets 100.000 visitors per year, and 500 people a day go up to Everest Base Camp, which is already over five kilometers high up (although people can start from a town with an airport at 2804 meters high).