I think 3D printers are close to the useful maximum. Most problems they have left are expensive to solve.
* One problem is rigidity/vibration. This is solved by lots of rigid mass, which isn't consumer friendly. It makes for a big, heavy, expensive machine.
* Another problem is the lack of feedback. This is solved by having accurate sensing of positioning. This costs money.
* Another problem is temperature management. This requires an enclosure and parts that don't mind the heat. This takes space and costs money.
* Another problem is extrusion consistency. This either requires very accurately manufactured plastic as an input, or excellent sensing of what's going into the extruder. This also costs money.
And most of these are polish on top. Like you can drop $700 on a very decent printer, or you could spend $5000 on one that mostly does the same thing, except is less fiddly because it's got a lot more steel and sensors in it. That makes sense if you're running a business, not so much if you rarely want to make stuff out of plastic.
Some of these are being slowly addressed in quite unorthodox ways. Eg, some sensing issues are being addressed with fancy motor drivers that can tell when the motor has gotten stuck.
There's also that resin gets way better precision and fixes many of these issues for way cheaper. It's got its own downsides of course, but it does mean that the amount of people who really need a very solid FDM printer is smaller than you might think.