In short, your comment doesn’t apply to the topic or Lutheran practice.
Permit me to disagree with you. While what you say is true for the bulk of the major lutheran denominations (based originaly on ethnic lines), what I said holds true also. Many divisions were caused by Scriptural disagreement (and when you believe in Sola Scriptura, you must follow what you think the Scriptures teach, well… your interpretation of it anyways.)
Some examples;
The AALC broke away from the ELCA when the merged with the LCA over doctrinal issues. Nothing to do with ethnical origin of members, but Scriptural disagreement (yes, even though they both hold to the Book of Concord (for non lutherans, the Book of Concord is a gathering of the lutheran confessions, apologies, creeds, etc).
The Augsburg Lutheran Church separated from the ELCA when the ELCA established full communion with the Episcopal Church (that agreement included a clause to move the ELCA towards episcopacy, which ALC members did not agree with).
The Augustana Catholic Church (yes, it is a lutheran body) which separated from different church bodies as they wanted a more anglo catholic approach than the regular lutheran church bodies currenlty had).
The Conservative Lutheran Association was formed by breakaway churches from different lutheran bodies over conservative/Liberal issues.
The Lutheran Churches of the Reformation is a very conservative group that separated from other very conservative church bodies (which they considered too liberal).
The Orthodox Lutheran Confessional Conference separated from the Lutheran Churches of the Reformation as they thought it was moving too much towards liberalism.
The North American Lutheran Church broke away from the ELCA and ELCIC (Canada) as they tought they were too liberal in their practice and scriptural doctrines and the LCMS too conservative, so they are more what they consider a centrist group.
The Protestant Conference (Lutheran) broke away from the WELS after a intrasynodical controversy and doctrinal disagreement.
The United Lutheran Mission Association broke away from the LCMS after a disagreement about missions and conservative/liberal practices.
I could go on, but you get the idea. The fact is that most of these breaks occured over doctrinal disagreement (even though they all claim to follow the book of Concord). While it is true that the major synods were formed over ethnic origins, all the breaks above had more to do with side effects of Sola Scriptura and self interpretation.
Feel free to disagree, but as I spent a few decades in Lutheranism, I know that it happens there too. (not as bad as other protestant denominations, I agree).