How would we be wasting your time? Are people forcing you to go to church, or are you constantly being bombarded with people trying to convert you? Are you complaining about the Christian Hubs on this site that waste a second or two as you have to click "hop" when you are hopping hubs? You might be living in a different part of the world than I am, so I don't know.
There are a lot of people that claim to be Christian but really aren't. Then there are people that are Christians but aren't very serious about it, or are new Christians and are still learning things. We're all flawed though. Anybody who tells you that they are perfect is telling a lie, whether they are Christian or not.
If I were to take a guess though, I would guess that a vast majority of people who say they are Christians really aren't that serious about it. You can see this by taking a look at some of the programs or ideologies that some of these churches teach - often deliberately going against what the Bible says.
As far as wasting your time, I don't know. I enjoy a good debate every now and then, but I wouldn't really want to engage with an unwilling participant. We all have to make our own minds about what we want to believe - that's what free will is all about.