Some (most/all) of them may have cheated to obtain their items. There are mods such as defiler which can increase the chance for a drop by x100. Also a mod that doesn't allow normal or cracked items (so more chances for a drop). Also shopping mods like shop MI.
Finally you can make your own custom map with whatever items you want.
Is this the best way? Or the only way to be powerful? No. But it is the only way to have the insane impossible to find items (super greens).
I personally find the challenge is ruined if I use mods or even use the caravan. Just keep killing the bosses that you can survive and the areas you can survive.
I tried an assassin and I thought it was a challenge but I know people have beaten legendary from scratch with it.
Which enemies are giving you trouble? Perhaps we can problem solve to find a way to beat them (different skill/gear/strategy)
PS I am equally impressed with people who cheat their gear as people who drive a car to complete a marathon
