This would be terrible for specialized hardware, such as assistive technology. Open source software doesn’t really exist for it because there is simply no interest.
Who says the software has to be open? It would be better for sure, but companies may be interested in selling software for assistive technologies.
Interest may go up if the barrier to entry lowers. Undocumented hardware is quite the turn off.
One reason for the blight of the blind here is the ludicrous complexity of the software, much of it comes from the ludicrous complexity and diversity of hardware interfaces, such that there is no competition and everything is terrible.
Most people however sharply underestimate the mountain of avoidable complexity we've accreted over the decades. I would situate it between 99% and 99.9% for personal computing. No silver bullet perhaps, but I know almost for a fact that there's enough silver dust around to gather 2 or 3 bullets.