The following answer is honest and not intended to be insulting, I just think sugar coating it makes it less accurate.
To beat any given game you have to be incredibly better than your opponents. It's not about beating them, it's about beating them and the rake. I don't care if that donk in a 2nl game just called you down with 6 high, if over a reasonable sample you were not winning against tables full of players like him, you are not ready to move up. You are not good enough to make a profit off of him.
I assure you that there is basically no one on this site who's any good, I include myself in the crappy, uneducated and ignorant group and I've spent probably tens of thousands of hours on this game. Don't convince yourself that you're better than you are, poker sites and t.v. poker do far better if they convince their audience that each one of them knows more than all of the fish, they frequently imply that the masses (the fish) are better than they are and should start making money from all of the fish. So you learn pot odds
, good for you. So you get a little more advanced and start assigning values to combinations based on circumstance and various streets, good for you. You still probably cannot beat the basic levels, not because you're unlucky but because you suck, you've overlooked leaks in your game. Small leaks and big leaks. You've miscalculated stuff that you think is right, it's costing you money. A whole ton of the basic principles you rely on are false. I can say this because it's true for everyone.
Sit down in a game. Play poker. Play a sample of say 20k hands, don't even look at the results during that time, understand that 20k is still only going to give you a hint as to your true winrate and don't adjust it emotionally in your favour, just take the results it gives as a suggestion. If you're doing well, move up. If you're not, you're not, accept you're not good enough to beat it, lose your pride and get to work learning it.
Stop complaining about the fish, all you're really saying is "I can't win, even with all of the help the fish are giving me, I still can't beat the rake and because I get emotional about that I play even worse!"