Valid points, but I'll once more point out that none of those, whether the historical forebears or the picaresque novel 'heroes' did it with the intent of dying. They wanted to get rich - either quickly or gloriously (or ignobly), but all agreed that wealth was nothing if you didn't get to spend it (and glory was nothing if it didn't make you rich or at least big enough to get free food from it)
Venturing into the unknown, and bearing risk is the reason why the endeavor is deemed heroic, because the adventurer is facing against what is deemed a foolish or impossible odds, spearheading new an untouched lands, in pursuit of an impossible but revolutionary feat, it is why succeeding awards fame, glory, and riches
It is characterized with bravery and recklessness, adventurers are not expected to survive the adventurer, in fact the expectation is that they will die, they are betting against the odds, and trying to probe the public wrong by acting against common moral advise, and going on an adventure, it is the rebellious spirit to achieve what was deemed impossible
Preparation and planning are part of being an adventurer, but facing danger and bearing the unknown is the common defining trait, even if motives and goals differ, the circumstances remain the same, which is why the JP wiki resumes adventurer by defining it as those who dare to try a challenge
No adventurer stops their quest for fear of breaking OSHA regulations, this holds true even to the realms of the political adventurers mentioned on the JP wiki, real life examples Thomas Edward and John Reed, are considered adventurers because their actions break common precautions, leading them to document periods of social strife and upheaval for the sake of journalism, even if doing so put them at risk of dying for their reckless actions, John Reed and Thomas Edward, probably took all the safety measures they could make, but the act itself of becoming war journalists and revolution reporters already marked them as reckless figures willing to put themselves in danger and face the unknown
And finally, this is also why the protagonist is made to go into the dungeon by himself, because this way the author can make him look good by making him the only character actually acting as an adventurer, he is disregarding safety and facing the unknown, in pursuit of an act of heroism
But i don't think that's good writing, it is cheap to conveniently put everyone else down just to have a guy forming an harem look good, while at the same time blatantly lying to the readers about an "adventurer's guild" that has to stop activities the moment a dungeon becomes prime field for adventure