To design a good user interface, you need a feedback loop that tells you how people actually use your software. That feedback loop should be as painless for the user as possible.
Having people to man a 1-800 number is one way to get that feedback loop. Professional user testing is another. Telemetry / analytics / user tracking, or even being able to pull out statistics from a database on your server, is yet another. Professional software usually has at least two of these, sometimes all four. Free software usually has none.
There are still FLOSS developers out there who think that an English-only channel on Libera.chat (because Discord is for the uneducated n00bs who don't know what's good for them) is a good way to communicate with their users.
What developers want from software isn't what end users want from software. Take Linux for example. A lot of things on Linux can only be done in the terminal, but the people who are able to fix this problem don't actually need it to be fixed. This is why OSS works so well for dev tools.