I never have and never will regard a Christian to be untrustworthy simply because he or she remains within organized church. The standard for that Christian and myself remains the same: faith that works by love.
While we all may be seeking God and while the God we seek must of necessity be the same God in event there is only one true God, it is impossible for every path to God to yield the same practical revelation of God.
If our faith in God is not at end of it all about our daily lives, our decision making rubric, focus of our lives, things we deem to be important etc., so far as I am concerned, faith or spirituality is useless, a waste of time.
Personally, I do not practice spirituality as some abstract thought at back of my mind over which I engage in intellectual debate with atheists, other Christians, Muslims etc.
I believe Jehovah Father of my Lord Jesus Christ has revealed Himself in the Bible and in history generally. I aim to harness as much of that revelation as possible for my spiritual development and for progress in my affairs in this life.
At the end of the day my interest in spirituality is eminently practical and pragmatic. In this sense, while my writings on spirituality are philosophical in nature, they are so precisely because Jehovah and Jesus expect people to demand some evidence in order to believe or in order to understand why I believe. My philosophical discussions at end of the day have practical or pragmatic objectives.