Her biggest complaints: bold/italic, and hitting return in a text box switches back to the default font.
To be fair to her, she's not what you'd call "into tech". Not clueless by long chalk, but not into exploring every inch of a product. I've offered to sit with her and go through some of the issues, but she just stick to her current workflow and bitch about it occasionally. Part of me knows what she feels like. A lot of people never learn vim, bitch about it when they find themselves on a remote server having to edit a long config file in vim, but still never learn vim.
In the case of Scribus, her biggest gripe isn't a bug it's a "WON'T FIX STOP ASKING"
The only time open source really works is where it happens to intersect with some commercial interest.
In fact, their commercial counterparts are and were so terrifically terrible, it put teenage me on a journey to discover better alternatives and how I discovered FLOSS in the first place.
What you probably mean is 'Professional' desktop applications are provably never going to match commercial counterparts. In which case, at least for Software Dev work, it hasn't been true for decades.
For creative work, commercial vendors have a tendency to squeeze out more from their customer base after a while, and that provides an opportunity to sneak in. FLOSS can also keep on trucking under the radar and suddenly appear to be good enough one day. Blender is an excellent example.