Yeah, you can't expect a long term win with say pocket pairs which you limp cause they make a set 12% of the time and say one time you make a set you will still lose if not even more. So it's 6 times you lose at least $1 which is at least $6. And I time you will win what? Maybe $5 IF no one folds your all in. That's -ev for you. Look at this with the BSS: 6 times you will lose $1 = $6. But 1 time ideally a guy's gonna pay you and you're gonna stack him and win his whole $10. Or at least you're gonna win more than the $6 cause you have high enough implied odds of maybe 200BBs. That's +ev.
With the SSS you should have not more than 8 VPIP, like 7 preflop raise, high went to showdown and high (like 70%) won $ at showdown. If you don't have those you're playing it all wrong and it's -ev.