How low the barrier is depends on how good is your prior knowledge. If you are a millennial that remember the internet before Facebook, it's probably very easy to understand the gist. For older people who never got into how computers work, or younger people that only saw the internet through smartphone apps, that barrier may be higher than we feel.

And it's hardly five minutes anymore. If using the official app sign up is as fast as Twitter or any other app.

That high barrier of entry is going to automatically keep out most non-techy people, and they tend to be a big source of entertaining content out there. Generally if you discount any bad UX as "takes only a bit effort to learn" that just means it's not user friendly and needs a lot of improvement.