This is the one big flaw I've seen in Stallman's philosophy on software. He's been thoroughly proven right I think about the dangers of closed-source (unmodifiable) software to user freedom. But I think his insistence that Free Software also needs to be freely redistributable with no payment to the author in order to be Free has greatly limited the resources available to build such software.
The FSF will argue "you can totally sell Free Software"[1], which ignores the fact that without any restrictions on distribution/copying, the fair market value of said Free Software rapidly drops to ~$0. It's not a viable business model. Companies have built alternate business models around soliciting donations, or selling support or non-free add-ons to Free software, but selling Free Software itself (at least as the FSF defines it) doesn't actually work in practice. (You can do it obviously, but it's effectively just a different way of soliciting donations at that point; the fair market value of the software is ~$0.)
The FSF will argue "you can totally sell Free Software"[1], which ignores the fact that without any restrictions on distribution/copying, the fair market value of said Free Software rapidly drops to ~$0. It's not a viable business model. Companies have built alternate business models around soliciting donations, or selling support or non-free add-ons to Free software, but selling Free Software itself (at least as the FSF defines it) doesn't actually work in practice. (You can do it obviously, but it's effectively just a different way of soliciting donations at that point; the fair market value of the software is ~$0.)
[1]: https://www.gnu.org/philosophy/selling.html