I think you are right. We share a common faith grounded in the 5 solas, however, after that there are some big differences. It would be nice if the Reformed churches made an effort to recognize how much of the flawed Roman system they brought with them, but at the core we share a common faith and I know I would be comfortable in any of the Reformed churches excluding the Lutheran church.
It’s not easy.
I have come to a place where I recognize and actually see working a Christ that is bigger than any human church organization. Now I might get a lot of disagreement for what I’m about to say, but people in even the most bizarre worship arrangement that still call on Christ by name, will in fact get Christ. Now the errors grieve God greatly, and the fewer the errors are the closer God will get (and conversely, the approach of God will purify the individual worshiper from the errors). This is what makes it possible to get a very godly Roman Catholic, for example. That person may in fact be ignoring most of the official doctrine and going along with the actual gospel.
Evangelical worship groups should use their freedom in order to embrace a better set of doctrines as God enables them to. God wants that. However they don’t need to get it perfect in order to be effective. They only need to have the perfect Christ, who is a real supernatural being, not something that men conjured up by having just the right doctrines in hand.
And so I affirm Christ and His power.
Personally, I’ve gone to a bible church for most of my believing years. I’m attending a Southern Baptist congregation currently. I like the relative freedom in both of those milieus, while still noting the places they could improve.
Lutheranism differs from "reformed" -- the former was founded through Martin Luther, the latter from Jean Cauvin or Zwingli
Would you be comfortable in the other groups that arose our of the reformation? Like the Mennonites or the Unitarians?
I once lived in a community where Lutheran was the only real option to hear Christ preached. Then the pastor changed out and that was pulled out from under us too.