It's a huge extrapolation to go from 'it's better to 3! or fold than call in this exact situation' to claiming this implies playing NLHE OOP is solved.

You're conflating semantic classifications with worthless poker platitudes. As Venice was saying, the nomenclature isn't important, it's just important to know how to play the hand. I understand your ad populum take on the matter, and I tend to agree.

Well yeah, it is. The statement sounded though as the money we make in general comes mainly from folds we get and to 3 in this situation would always be +ev, even considering if we miss, stab and get played back at.

That statement implies that every starting hand could 3-bet in this situation and be +ev.

I just thought it sounded like quite a big generalisation, but that said I have not even close to the knowledge Venice has. Hence my questioning

No, raising here puts V in bad spot. Come on, stop check calling and trying to just make your hand. Good play, manyt decent players bet fold K2 here, and definitely top pair type hands.

Just to clarify, I probably would have 3 bet pre, but if I did just call, I never would have called the flop. But given the spot you got yourself in, I like the turn play. I hope you showed your hand, it is the one benefit of making this play, getting a stubborn call, and missing.

What he said was, some players who raise wide also fold most of that range to a 3!, therefore we can profitably 3! vs. those particular players while never even having to cbet.

If someone folds 67% to a 3bet and our 3bet size is 3x, we are breaking even by 3betting with ATC and folding the flop. Up their fold rate at all or reduce our 3! at all, we profit.

So yeah, for NLHE is solved for this exact situation.

He also said, if this guy flats 100% of his range, we should consider folding instead. If we're OOP vs. a competent aggressive player, a slight hand advantage is not going to be enough to make money.

Most LAGs will fall somewhere between these extremes, which is why we can start by picking a value 3! range only and err on the side of overfolding OOP until we get a better idea of the way they respond to 3!. This kind of person is a good candidate for a 3! with Axss blockers for example, see how they respond. In live low stakes play though, it's harder to make these kind of moves because you have a bunch of stations in the game.

Anyway, point is, there is more going on in Venice's post that a suggestion to robotically 3! OOP.

Werebeer answered your questions well. Let me get into a little more detail.

I admit that I don't list every assumption I make when making a statement like "we can fold every flop and still make money if we 3bet." For myself and I'm fairly confident others, it is difficult to comprehend a complete range when making a decision. I find it easier to think of the worst hand he could do an action within his range. It is easier to think, "Is this player raising with KTo or not?" It becomes a gut check. As I stated in my first post, a 3bet becomes a possibility if the answer is yes. The reason is that competent LAGs learn quickly that when a tight player shows aggression back by raising, they have a real hand and aren't going to fold easily. LAGs live off of folds.

So what range is he going to assign a player that 3bets. Usually it is going to be really tight for most LLSNL players. Therefore, he's going to fold a lot of his range not wishing to play a big pot against a big pair that is unlikely to fold. Even if he know for a fact that you'd 3bet AQo, he's going to need to fold about 2/3 of his range to remain competitive. Probably more. Folding that much means we have an automatic profit, even if we fold everything on the flop. Since we aren't going to fold everything on the flop (we're not folding on a AAA or QQQ flop for example), we know we'll even be more profitable than that.

However, if he starts believing we're 3betting ATC, he's no longer going to be folding his range. He's going to be 4betting to get us to fold. So we can't continually 3bet everything. It isn't going to be a sustainable strategy.

Now if he isn't raising with KTo, the math begins to shift. He's opening a smaller range. Competent LAGs love position and often aren't going to have much different an opening range than competent TAGs UTG. If he's raising no worse than KJs (which is still pretty wide), he isn't going to fold even 1/2 of his range. Now we have to win additional money post flop oop. We'll need an ace high or queen high flop to even be ahead of his range. If he can beat top pair as you point out, we're going to lose a lot of money.

Out of position, I don't like to be in a situation where I'm going to have to fold on the flop a lot and even if I hit, I'm playing a RIO hand. Therefore, I prefer the fold pf. My goal in poker is to either being in charge of the hand by raising/betting, trapping with a hidden monster or calling with a hand that is going to improve to a big hand. AQo is not going to be hidden, nor improve to a big hand often enough to just be calling with it. There's no shame in folding the best hand in a small pot when you only beat the bottom of the villain's range.

Thank you WereBeer, Venice and thank you all for your time.
It's very nice to be able to learn from you and you managed to clear some stuff up for me. There'll probably be a lot more posts from this swedish donk
Thank you!