It's not that hard to learn how to get into the secret "technician-only" settings screens on existing CPAP machines. They can't be that dangerous. I've fiddled with mine (the technician told me how) and the worst I've done is give myself an uncomfortable night's sleep. It's an airhose with a not-particularly-strong seal gently squirting air into your nose, not a chest tube.
They don't need to. You want to set the machine to the lowest pressure limit that ensures you sleep well and are comfortable. This progress can be objectively measured since the machine counts apnea events. Both of these are easily surfaced in the UI.
It's no different than setting the volume on your headphones to a comfortable level. And it is not some fiddly arcane art that requires a medical intervention.
The danger there is that there is more to it than just pressure.
Many of the defaults, at least for me, actually make it much harder. Like, my machine by default ramps up the pressure slowly... which I find quite uncomfortable... I am on the higher end of the pressure range.
I run in APAP mode, with a rather narrow range of 17-20. (20 is the most typical machines can run.. some bipaps can go up to 25). Anything below about 15 feels like I'm breathing through a straw.
Humidity setup is quite important as well, and often paradoxical (lower setting = effectively more humidity, as water capacity is limited and on higher settings pretty much all of the water is used in the first couple of hours).
Now, none of the professional people involved helped or guided me to any of that. My initial sleep stufy (in person, not home, this was ~7 years ago) came up with a static pressure of 13.5. That didn't work well at all, as stated above. That said, if I wasn't a techie, I doubt I'd have figured any of that out.
The market there has mostly eliminated titration in the US. Instead of determining the ideal pressures in a controlled environment, APAP machines are prescribed instead which monitor for events (where you may have stopped breathing) and increase the pressure in turn.
This is why such a large number of sleep studies are home studies now - it is cheaper to spend $200 more for APAP then pay for an overnight sleep study center
I used to work in an office next door to a CPAP place and the few interactions I had with their customers over the years did not suggest that the average person could figure out how to operate one.
The current expensive and very slow process getting a machine has some, but very little, to do with safety.