The problem is that most normal people (HN is not normal - mostly for the better) don't even understand what sideloading is - let alone actually care.
How can we fix this?
(aside from making people care - apathy enables so many political problems in the current age, but it's such a huge problem that this definitely isn't going to be the impetus to fix it)
Another approach I wonder about is single task specific hardware, like a GPS unit or media player, what tasks have developed over the past ~18 years within the mobile ecosystem and are mature and not rapidly evolving enough that they can be unbundled to their own devices, and desirable enough to stand alone that there's a market for it.