My personal opinion is that System76 isn't really targeting personal users with their desktop line, though, but instead is more focused on professional users. For example, I built my own desktop computer at home, but if I needed one for work for doing ML or just to have the increased compute over my company-issued laptop, there's no way that my organization would sign-off on letting me spec out my own parts from Newegg and spend a day or two building and testing the system, then trying to install NVIDIA drivers on Ubuntu.
What they would (and do) sign-off on is a one-time purchase of a desktop from an approved vendor for that desktop, which comes with out-of-the-box support for the NVIDIA GPU I've selected. That's more the niche that I feel System76 is really filling.