Loose passive games are in theory pretty easy to beat, but you need to be patient.
I assume from your post that you play Sng's.

I would say that you want to limp with hands that work well in multiway pots (suited connectors and such)

On hands that you want to isolate you have to bet very agressively. If everybody calls 3BB bet 6BB, if everybody calls 6BB go AI with strong starting hands.

Bluff very rarely until you are down to 3-4 people.

On multiway pots with 5-6 people in the flop be very careful with TPTK, low two pair etc.., you need strong hands when so many see the flop.

Don't be discouraged because they don't play 'proper' poker. For one thing Loose/passive is a beatable game, and more importantly, a good poker player learns to adjust his game to the other players