We'll have to agree to disagree.
You may well be right, but I will continue to say that I think D&D should specifically
not (try to) be a "realistic" game, because it never has been and striving for it has only ever made it worse at what it does well, IME. That is a major reason I drifted away from D&D around 1983 and only really came back to it with gusto in 2008, in fact.
Hit Points was a means to an end. Something had to take into account, for lack of a better term, life force.
No, it really didn't - and doesn't. The best realistic RPGs don't use hit points - it's really simple when you open your mind to the idea that they are not merely optional, but poor at conveying how wounds work.
Check out HârnMaster; the only thing even similar to hit points is the "bloodloss" mechanism, where if you lose enough blood you die. Other than that, sheer number of wounds won't kill you (although it might make it more likely you'll die - a subtle but important difference).
Classes can easily be called professions, which we do have in real life: Soldier, Nurse, Detective, and cubicle-dwelling customer support dude are all classes. And again with levelling, means to an end.
I have been a professional all my life - it's not my "character class". It's not even close. The "careers" system in Warhammer Roleplay or Traveller would be closer to "reality". And character class is manifestly not necessary for a roleplaying game - many, many RPGs don't use them.
A system can plainly be both and yes, D&D should be that system as it has been in the past and has and can lend itself easily to all styles and plenty of genres.
I don't believe
a system can ever cover both angles well, no. That is not what they are proposing for D&DNext, however; the "modules" that are proposed will make it actually a range of many systems, all of which can be constructed by a gaming group using the elements ("modules") provided. The possibilities here are a lot less straightforward to predict; maybe it would be possible to combine different elements around a core system to support such radically different play styles. The D&DNext I see in the current playtest system, though, won't ever do "realism" well - because of just the elements I have listed above. If I wanted a system that suited realistic world modelling well, I would start with a system that didn't use hit points, classes or levels (quite apart from anything else).
Edit: to be clear, I don't want to
stop people trying to play a realistic game using D&D systems if that's what they want. I think it would be a crazy thing to do, since it would involve hobbling the attempted aim from the start - but if folks want to do that, good luck with it. What I would object to, however, would be the design team making "realism" a design goal. The reason for that is simple: every time it has been done in the past it has generated clunky, crude, broken and confusing systems that make the whole game worse at doing what it's actually good at - a game of fantasy teamwork overcoming fantasy challenges.