If Poker is a game of incomplete information, why playing in a pool where everyone is face up does not yield you 30bb/100?

I've been playing poker all my life, as a ****ing NIT, and I've always been flirting with a 1bb or 2bb/100 win rate, up to NL200. When the game changed, and everybody went full NIT, i simply quit, while the rest kept playing and went broke.
After several years I reinstalled Pokerstars and played 200K hands on zoom 10, always like a miserable Nit, and made 0,9bb/100. Then I wondered "Wait a second. Nobody 3bet bluffs, 4bets are KK+, nobody bluffs, nobody slowplays, bet sizings and timing represent the actual strenght of the hand, why don't you try to play ACTUAL poker and have a positive red line for the first time in your disgraceful NIT life?".

I played 40K hands, I have a positive red AND blue line, my stats finally look like the stats of someone who actualy knows what he's doing, and my win rate is..........2,9bb/100.
I know that 40k hands are nothing, but I'm on a 16 stacks downswing and I keep wondering how is it possible to lose 16 stacks against 5 players with their hands face up.
Why, mathematically, the only way to win big at this game is having 1 whale at the table who stacks off with K3 off, while having 5 players who literally never bluff is almost a losing proposition?

I guess 9bb/100 in rake plus 3bb/100 in winnings is the absolute maximum you can achieve vs NITS, but why is that so? Is playing (badly) a strong range preflop enough to not lose more than 12bb/100? Well, now that I said that outloud, it makes sense. Has someone used a solver to analyze an enviroment with 5 NITS and see how much can you make and why?

What stakes? I'd say find a better site or learn a better game.