Checking the box of ideals doesn't mean that open source software is off the hook in having to compete on features. Regular users do not give a rat's ass about source code being open; it's an extremely abstract concept if you're not in the field. All they care about is free as in beer. Matrix can either target the niche demographic of the highly technical, or it needs to level up on usability to reach a wide audience.
The number of people who have tried LibreOffice, Gimp, etc is probably orders of magnitude higher than the number of actual daily users. If these software applications were businesses, their exec teams would have been fired many times over for the atrocious churn. Free as in beer is an excellent foot in the door, but it's wasted time and again by huffy developers who don't know how to create good UX and who won't open the door to good product people who want to help out.