I think it is an extra-Scriptural interpretation to go from "traditions of men" to "All traditions are merely traditions of men." In other words, that interpretation is NOT "sola Scriptura.
We can also look at any "tradition" created after the Bible was written was NOT a tradition that the Bible spoke of, and was just an elaborate contrivance of man and given "authority" BY MAN.
God gave us his word to read. To instruct us, to convey his love for us and to us.
Much like a person sends a love letter to another. A person can read it for what the writer intended, but hug it regularly or kissing it or waving around your head 3 times, pumping it up and down 5 times and back and forth in front of you 6 doesn't make it ANYMORE meaningful. The writer might think its cute or endearing, but still meaningless. Same with any manmade traditions.
God gave us his Word. He also gave us (our jewish bretheren) certain traditions. Anything else is man made.