Yet, I think one big reason why non-profit solutions are so unpopular is not primarily about marking, but about the terrible, truly terrible UX that most non-profit projects have.
As far is I can tell this has (mostly) nothing to do with constrained resources and just with the extremely technical perspectives of the maintainers.
Element is a laggy Discord clone. Signal is years behind other messengers in terms of features and general UI quality, Thunderbird is stock in the early 2000s, same as VLC, and I don't know a lot of serious artists that are using GIMP.
So, even though this is surely not the only reason why open source projects are not widely used, I think it's a huge contributing factor.
There are shining example s though, like Blender, Godot or Mastodon, that are truly open source and have a great set of features paired with nice UX and I don't think they're doing too badly :)