My "bad" is less about preferences and more about giving a clear indication of the route that was picked.

To illustrate, let me start with an example that predates Google Maps. I was cycle touring through Western Kansas and saw parts of "old-40" that paralleled I-70. It seemed like a reasonable choice, though my paper maps disagreed on how much of the route was gravel. I (mistakenly) assumed that roads generally went from being unpaved to getting paved and hence assumed that the map that showed ~8 miles of gravel was more likely correct.

Turns out, Grove and Trego counties had found maintenance of the old pavement was too much trouble and hence had torn up old US 40 in their counties and converted it back to a gravel road. Rather than 8 miles of gravel, I ended up with ~18 miles of good hard-packed gravel and ~12 miles of soft sandy gravel road. If I had known I might have made a different choice.

Similar idea with Google Maps bike instructions. I don't necessarily need it to avoid gravel roads, but instead give a clearer indication of the routes that it has picked. A similar example from my current travels: go from "Heroica Mulege, Mexico to Ciudad Constitution, Mexico". Auto route is ~282km of paved roads. Bike route is ~274km of which I'm guessing much less than half is paved and water re-supply points are very limited.

Last week I cycled the auto route in four not too difficult days of riding (18.5 hours riding according to Strava). I expect the off-road riding through Baja would have been much tougher and certainly longer than the "15h 25m" that Google Maps bike route gives as a time estimate. So the "bad" isn't that there may not be people with preferences to go bikepack back roads in Baja, but that Google Maps bike instructions doesn't give clear indications what parts are bike touring and what parts are bikepacking and it can make a big difference.