writes:

Flying solo in an aircraft that requires a crew is unsafe.

Not necessarily. If an aircraft can be flown by one person but the
manufacturer has not applied to have it certified for single-pilot flight, it
isn't unsafe, it's just illegal.

Flying anything without doing complete flight planning is unsafe.

Define "complete."

And both are illegal.

A flight plan need not be complete to be legal. Indeed, you don't have to file
anything at all for VFR in the U.S (usually). And how much planning you do is
up to you, as long as you don't seem negligent in the event of an accident.

Safety is a separate issue.

I try to simulate both, but again it depends on the circumstances and my mood.
Filling out paperwork is not a fun part of aviation for me.