With much of this, I actually agree. That said, IME by far the biggest overall motivator for adventuring is Moar Wealth; sometimes just to have it and watch it accumulate and other times to do something useful with it. What this means is that as DM often all I have to do is dangle some loot - or the potential of some loot - in front of them and away they go.

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And IME wealth is the absolute last motivator for most of my players. Even when they make wealth motivated characters, they make them with the intention that that is a character flaw they need to overcome.
Corollary motivators can include a sense of responsibility (for some characters), defense of themselves or of people/places they care about, curiosity and-or research, and similar. In a very few specific cases the pursuit of fame and-or glory is a motivator, but this only usually happens if-when a player has long-term political or monarchic plans for a character (quite rare) and is trying to use its adventuring career to lay the groundwork for such.
Those Corollary motivators are the PRIMARY motivators for most of my games. Even the Fame and Glory motivation is something I've seen, never for a long-term political gain, but for "I want to be known world-wide, like Heracles or [insert other character]"
As far as I reasonably can I try to make the bolded untrue. Yes, combat is highly abstracted and hit points even more so; these are unfortunate but necessary evils in order to make the game playable. But where I can, I have a (fantasy-)physics-based underpinning even for things like magic, fantastic creatures, and so on.
That is not the design of the game. You trying to make it the design of the game does not change how the game was designed. And the abstraction of HP is key to my point.
First off, I'm not all that concerned about breaking these sort of genre conventions, in that I want a flatter power curve anyway such that a "low-level" creature remains a potential threat for longer while at the same time low-level PCs have a slight chance (as opposed to no chance whatsoever) of pulling off an upset victory over something way above their pay grade.
Second, if a situation would be approached with caution in reality then I'd also like it - at least to some degree - to be approached that way in the fiction, if only because that's what the characters would do.
Except my entire point is that IS NOT what the character would do. John Wick doesn't go into the nightclub full of mobsters with nervous trepidation because he honestly believes he is going to die. Neither does James Bond. Neither would Conan entering a den of thieves. These people are not actually scared for their lives, they do not actually believe they are going to be killed in the coming fight. And mid to high level PCs are the SAME WAY.
And while you may WANT a flatter power curve, you cannot look at the current design of the game and honestly think that a single kobold is a serious threat of death to a full hp PC past level 2. It just isn't. A dozen of them might be a threat, but that is the weight of numbers. And that makes sense, because it isn't the individual strength that matters at that point.
I can't model the world 100% true but I can always describe it better and stand ready to answer whatever questions the players might have. That said, if there's a hidden hazard and they don't take precautions I don't see it as my job to tell them about it; and even if they do take precautions there's always a chance those precautions won't be good enough due to the luck of the dice.
Your job to tell them about it? No. Your job to foreshadow it? Yes. Especially, again, if the point of telling them about something is to tell them not to go there yet, you need to accurately foreshadow the threat. And this isn't a matter of describing it better. You can't know if the shortage of wool in the western kingdom changed the merchant routes which pushed a merchant eastward, where he saw a herd of owlbears fleeing the forest to the south, which was only possible because the normal fog that rolls in from the lake didn't roll in that morning, because... you can't do that.
Just as an IRL example, thing that happens ALL the time. I recently joined a forum site, where I learned about a book series from the 70's. Then, I was watching a new youtuber who was in no way connected to that forum or the subject matter of that forum... who referenced the exact same book series. And again, this happens constantly. Because the world is massively complex and intersecting. And you can't actually model that in the game. So, it is always preferable to create coincidence on purpose so that people can learn information, instead of deciding that there is no way they could know about something.
Yes it was. Once on the move, for a short time those Ents became the most powerful army in the world; the self-preserving thing for the Hobbits to do was to stay with said army and let that army protect them.
Not stay far away from the fighting where a catapult couldn't accidentally crush them?
Indeed, and that's down to those two having - and sometimes displaying - less than stellar Wisdom. They both swore alliegiances to monarchs who then called their promises in, and found themselves in the field whether they wanted to be there or not (though in Merry's case he did want to be there - high courage, low Wisdom).
See, but calling that stupid (less than stellar wisdom) just makes my point. Those stories were not told because the characters proceeded with an abundance of caution, measuring every step they take against a potential horrible end. And that's why we like those stories. That's why we want to recreate them.
I'll concede this one: Bilbo's courage outweighed his self-preservation instinct on numerous occasions.
After they stopped in Rivendell they were on something of a time crunch; and their lack of info-gathering about Mirkwood did cause them lots of headaches.
And that was what made the adventure story. That's what made it popular and allowed Tolkien's works to proliferate. Removing that factor entirely defeats the entire thing that caused Tolkien's works to inspire DnD.