"...people...are...dependent on...other people..."

Society is people. People have always been dependent on society. This is why overlords have been able to parasitize collective production, because society has always been mutually dependent, even before the advent of agriculture.

Society has been egalitarian for the majority of time that humanity has existed. Collective industry has only been practiced for a few millenia. Until collective industry arose, overlords had no ability to parasitize it, because it didn't exist. Egalitarian society isn't novel, or potentially unworkable, because it has been how humanity existed for the majority of the time it has existed.

Something that makes it possible for non-specialists to use specialized devices is automation. Open source, as you point out, enables such software to be used without royalties, and machines manage themselves while still being able to be tweaked by users. I have a 1980 VW pickup with mechanical fuel injection. Electronic fuel injection is able to be tweaked with software, which is much easier than altering the function by adjusting the mechanism.

Regarding circular dependence of specialists, this isn't new, and has been a feature of centralized society since it arose. I have never intended, advocated, nor claimed that human beings can be lone wolves, but rather that society does not need overlords, and in fact suffers from their parasitic losses and self-aggrandizing control. Free people can work together to produce mutual felicity, and for most of the time humanity has existed that has been how society has functioned.

Regarding the lack of personal association with people we depend on, that is the present condition. Dunbar's Number is the amount of people we can have personal relationships with, and is likely the result of Stone Age people being limited in the size of local population by local resources.

Having the means to produce goods and services ourselves does not make us islands incapable of associating with one another, and does not preclude specialization and trade between each other, nor obviates larger cooperative undertakings. If a village 3D printer is possible, then a village full of 3D printers is equally possible because the specialists capable of understanding one 3D printer is capable of understanding each of 3D printers. However, since 3D printers are essentially automating positioning the printhead, it's not particularly different to use myriad materials with 3D printers. What's different is the printheads and environment in which the different materials are usable. There is essentially no difference from room temperature in that environment for many materials, like concrete, PLA, and frosting, while steel, glass, and nylon require higher temperatures, and ice, CO2, and etc., require low temperatures.

Using 3D printers, once the technology matures enough so that they are mostly automated, won't be much different than using indoor plumbing.