The plane JFK jr. was flying almost certainly had a good autopilot. Even though he was not instrument rated, he should have known how to use it. He could have made a safe descent on autopilot.
In the Bryant crash, it appears that the pilot made a bad decision to try to fly visual in marginal weather instead of on an IFR flight plan.
Inexperienced pilots panic and become disorientated. JFK Jr. was not a rocket scientist, and he had just enough training to be dangerous.
It was not for naught that the Beechcraft Bonanza earned its infamous moniker: The Doctor Killer.
“And as you know, in general aviation aircraft, there are often going to be people who are flying airplanes for which they are not properly trained or they try to fly them in an environment for which it is not certified and capable of withstanding. And so we ended up taking a class of people epitomized by physicians, putting them into a high-end airplane epitomized by the Bonanza, and every now and then, when there’s a crash, there’s a pretty good correlation between those two categories.”
https://generalaviationnews.com/2017/03/29/the-doctor-killer/