The bottleneck, for the most part, is actually being able to test them. Even a translation by a skilled engineer is liable to have issues if they don't actually have the hardware to test things out. Linux's driver support is built out mainly by people doing that, either hobbyists scratching their own itch of hardware they own or manufacturers contributing drivers for their own hardware.
(It's also why regressions are pretty common: it's completely infeasible to test all of linux on each release, some people test some parts of it, but it's all very ad-hoc, very little is automated, and it's not at all unified)
(It's also why regressions are pretty common: it's completely infeasible to test all of linux on each release, some people test some parts of it, but it's all very ad-hoc, very little is automated, and it's not at all unified)