Gaming

In addition to what other people have pointed out, I'll also add that most decent randomizers are very configurable -- you can usually make things as random (or as not random?) as you want. And typically you can also get a "seed solution" which will tell you exactly how to complete it (or if you've configured it to allow impossible seeds, it can tell you if it is even possible to do so). And there are many more options to use besides that. If you only want certain aspects or elements or sections of the game randomized, or you only want them randomized in a certain way or according to certain rules you can usually do that too. And you can usually either search for or tell it to generate specific seeds that will give you certain things early to give prompt access to the whole world if you want. These are called "open" or "very open" seeds. For speedrunning they can even be a significant challenge, as there is little guidance on where you need to go to get the next item when the whole map is almost immediately unlocked. The opposite, so-called "linear" seeds, have a very direct a->b->c->d progression path (much like the original game probably did) where as soon as you get an item, you know exactly what your next goal must be because the particular combination of items you possess might only give you access to one new location each time. But you may only realize this once you become intimately familiar with the game mechanics (and sometimes the randomizer's mechanics too).

Randomizers are really powerful tools for replaying a game you've otherwise mastered but they're not intended to only be hard. Sometimes they're actually very easy, especially if you tune them to be. And that's part of what's fun about them, the flexibility of being able to play some of your favourite games again in ways you always dreamed of doing, or ways that you never dreamed of doing. It's not just a challenge it's also a sandbox. It allows you to do new things that you never would've been able to do in the game without cheating, but it doesn't necessarily remove all challenge the way cheating normally would.