I think your post has some of the answers.

God is a God of order. Christ organized a system and structure to spread His gospel to and develop (apostles, seventy, missionaries) as many people as possible. Without an organized church we may not have Bible today. Do churches sometimes become corrupted? Yes. Did conspiring men alter the Bible? Yes. But a lot of truth made it to our day, and without medieval churches I suspect we’d have no Bible.

In our day it’s tough to know which churches are not corrupt, which don’t manipulate for gain. Again I think you allude to the answer: God will let you know in your heart. Now, it takes time, research and even attendance at some of the candidate churches. But ask Him. He will let you know in His own way.

Being able to lift and be lifted by other like-minded people is a huge blessing for me. We lean on each other for strength. There are other advantages as well. You don’t have to have a fancy church for them, but someone must organize the structure (not necessarily physical), system, schedule, etc. My church has no paid clergy, we all organize it ourselves.