I agree with you about discoverability, but in practice I find that tasks aren't completely new every time, there usually are common principles. With usage, you kinda get to know what is and isn't possible, even if you don't recall the precise details of each and every command. So you can look them up, knowing more or less what you're looking for.

On Linux, `--help` usually... helps. Or there's the man. On Windows, the MS docs are usually usable to find things.

Of course, it may not work 100% of the time, but I find it's a question of philosophy. I'm not a Windows user, so I generally approach it with a mentality of "it would be nice to be able to do this, let me check real quick if there's a way". I usually manage to not have to click around for two hours when I have to do something repetitive.