Remember, science is supposed to be the open minded investigation of observed phenomena as opposed to taking a fixed position based on a logical sounding theory.
Yes, in theory, since bits are bits, a DAC should be able to render perfect sound (forever, yet) if the bits are correct. But if you can hear what a good streamer does, that can prompt an inquiry into why, instead of getting stuck on how a DAC "should" be.
In practice, to my ears and many others, you get better sound by reducing digital noise with all possible strategies, including streamers/renderers that reduce noise presented to the DACs digital inputs. Remember, you can have conducted noise over the digital inputs, AC power noise, radiated noise from other equipment, noise generated by the equipment itself, etc.etc. It seems that given todays SOTA,, you can't completely eliminate noise incoming to a DAC or even noise generated by the DAC itself. Instead, you do whatever you can to reduce noise wherever you can. The streamer was a big discovery and now people are finding that network switches can help (probably by reducing the ethernet noise reaching the streamer among other things).
All of the streamer companies are trying to reduce noise, they just do different things. MSB now has the digital director to keep noise of their DACs. Taiko is well loved on this forum, they use a super fast CPUs (so they can be mostly idle) and many other expensive strategies (the case for example). Antipodes separates the renderer from the streamer so the more CPU-expensive streamer functions don't impact the renderer. And lots of these companies are making their own apps, with the benefit of generating less load on the CPU. Then you have CAD which sells noise reducing passive ground controls as well as a streamer and DAC. Finally lots of companies making lower noise Ethernet switches / filters to keep noise from reaching the streamer, let alone the DAC.
It all seemed unlikely to me, given my software engineering background and development experience, but its audible, so I buy the stuff