Free Software originated in the hacker community—which is a community of developers developing for developers. It's always struggled to extend those values in a way compatible with the rest of the world. Notice that developer tools like GCC or Linux are the big success stories of Free Software, whereas end-user tools like OpenOffice or GIMP have always been kind of…meh.
That is akin to saying that democracy is fundamentally valuable only for politicians, because only politicians can use the freedom it gives.
That is simply completely wrong. You don't have to be a developer yourself in order to benefit from not being dependent on a monopoly. The fact that you can buy development work on the free market benefits every user of Free Software. The fact that the code of Free Software is easier to inspect benefits every user of Free Software.
There is no need for everyone to be a politician for democracy to be generally valuable, there is no need for everyone to be a car mechanic for freedom to repair cars to be generally valuable, and there is no need for everyone to be a developer for freedom to inspect and change software to be generally vaulable. Those freedoms are what enable free markets instead of monopolies.
That is not really true.
For one, even users of purely proprietary software do benefit from the work that developers of Free Software do, because the market pressure exerted by their presence in the market does affect the pricing and quality of proprietary offerings. While that is an indirect effect, it does not in any way require "enlisting a developer".
Also, in order to have a free market choice in who you hire to do development work for you, you don't need to enlist a developer. That freedom of choice is every user's immediate freedom.
> The closer it gets to a “pure” user problem, the less incentive there is for developers to work on it, and the worse it gets.
But that has nothing to do with whether it's a "user problem", but only with whether it's a problem of people who value their freedom. If a user values freedom and thus invests in it, such as by paying a developer for doing some work for them, then they will get just as much freedom as developers who value their freedom and for their reason invest in it. The problem is not that they are users, the problem is that they are unwilling to invest in their freedom, and instead expect others to invest for them.
The problem is the expectation that developers invest in the freedom of users. Developers will invest in their own freedom first and foremost, obviously. If you expect developers to invest effort into solving problems of non-developers, you should also expect non-developers to invest in developers solving their own problems. Like, you should expect users to pay developers so they can work on stuff that is of no importance to the user.
Substitute software freedom with open source and I'd agree. But software freedom is a whole other thing that is valuable to non-developers. Proprietary software can cost money, require subscription fees, make older versions no longer available, add all sorts of licensing costs like per CPU licenses, restrict features to "pro" versions, etc. Those are issues that affect people (and large companies) that will never read the source code.
Free software is about user freedom, OSS is just a means to that end.