1- We are not here to judge other people. Just be dan lkaf zchus that its appropriate for those people who daven at those minyanim at their current level of observance.
2- If you dont daven shmone esrei with the tzibbur you miss the value of tefilla betzibbur. I once heard that if you dont start while the tzibbur is still within the first three brochos you already lost tefilla betzibbur, but I dont know the source for it.
3- See #2 above. Davening with a minyan generally refers to shmone esre. There is a whole siman in shulchan aruch on which parts on pesukei dizimra can be skipped to ensure you start shmone esrei with the tzibbur.