No, I don't believe it's a sin to not be a member of an organized church body, but as THE church, we are the body of Christ. Being a body, the church is made up of different parts that all have a role to play in the big picture. Some of us are preachers, and some are teachers, and others are gifted to be a church secretary or even a janitor. The point is, we all have a role and a purpose in the body of Christ. We have to be fed the Word of God yes, and that can be done in a group setting of any kind. Then comes ministry, which we do everytime we walk out into the world on a daily basis. But, then there's our duty to the body of Christ itself. If my bladder decided one day it didn't like my kidneys too much and decided to leave and go do it's own thing, I would be in pretty shape, eh? The same goes for the Body of Christ.
and I know exactly how you feel, Defending, about how some churches conduct things and get their priorities mixed up. What we have to remember is that the Word tells us not to place our faith in man. People will fail and disappoint us, and make us just downright furious sometimes. All we can do is pray for those people and continue to do our best by contributing our own gifts to the greater good.
As far as your own church situation goes, I can't tell you what to do except just keep trying to find a church to get involved with, because you never know how your contribution might bless even ONE person in any church at any time. I was studying the early chapters of Revelations today, and saw exactly the pattern of behavior your referring to in some of the churches Jesus had John write to. But, the Word mentions that even in the midst of those churches where there were problems and disorder, there were those who remained faithful despite what the others were doing. The point here is that there are no perfect churches. Every church has its issues, but we as individuals are responsible for our own behavior, so not everyone in a mege-commercialized church is going to be greedy and prideful. Some of them are just faithful, churchgoing folks who are contributing their gifts and talents to the body of Christ.
No stumbling pilgrim in the Dark, the road to Zion's in your heart.