Which is a different way of saying that most computer UI still sucks for most users. I agree, and I think that one of the key reasons programmer-y people are successful at navigating computer tasks that stymie the proverbial grandma is this: faced with a question about how to accomplish a task inside some UI, we're just inherently more likely to follow a similar train of thought as the person who wrote the program in the first place, and reach the correct conclusion. (And case-sensitivity in a username is exactly the kind of keen (textual) detail that we're both wired and trained for.)

In other words, we're just iterating on trying things [as xkcd observed][0]. The key is that inside that first decision box, locating an action to try, we have a huge leg up on the "...which looks related to what you want to do" part. I sometimes describe this as "knowing how computers think", but really it's knowing how the people that wrote the program think.

Not that it's an easy problem, but I think we still have a lot of work to do as a field, to make stuff accessible to people whose brains don't follow the same patterns as ours.

[0]:https://www.xkcd.com/627/