The entire problem starts and ends with this term. It is ambiguous, personal, localized, fluid and case-dependent.
What is friendly to one user, is insulting to another. What is friendly to me at 10:00 in the morning is frustrating when I have a presentation in two minutes. What is friendly to an American pensioned welder, is insulting to an Iranian accountant.
Just to explain why I love Linux so much - when I'm in Gnome, I'm not bothered by any alerts or notifications or popups or sounds or ads or anything! It's a silent, stable, good looking desktop that runs my programs and doesn't get in my way at all. It's amazing! I truly love it.
I think Linux DEs are fine, it's just that the default config / on-boarding rarely asks what the user wants and what they need.
More distro/DEs need to incorporate UX/Desktop Layout Switcher, like Ubuntu Budgie, Zorin OS (Gnome, XFCE), Manjaro (Gnome, there are plans to do KDE as well in the forum?), and FerenOS. It'll solve the issues of personal preference in UX, as people could just one-click choose what feels/looks the best for them.
I personally don't mind taking a few hours setting up the UX I want with Fedora KDE, but I doubt most others do.
I tend to disagree here. I recently switched back to MacOS after years of running both. The DEs on Linux are just one generation behind. Things have gotten better, but macOS and to an extend Windows are ahead.
Linux DEs would be well advised to onboard more graphics and UI experts to make them more user-friendly and stable. Desktop metaphors have more or less stabilized and it's counter-productive to have 5 takes on the Linux-side alone.