It doesn’t appear we’ll be able to agree on this, but the definition of supreme is to exist on a higher level, and in these teachings, this supposed entity ein sof is on a higher level of existence than the God of The Bible. These teachings were conceived centuries after The Bible, as well, which lead many to believe they are the blasphemy, not The Bible. Obviously the debate won’t settled here, but my my framing of it still appears accurate to me. Have a good day.
Your framing is based on profound ignorance. There are so many subtle layers I left out to make my explanation more understandable. The ein sof IS simply another aspect of the same G-d who rules over the universe. It's not a different or "supreme" G-d. Same one. Here's a suggestion: don't try to understand something really profound and sophisticated of another religion, something which takes many years of extensive study, based on "somebody's" posits. Someone who obviously lacks these years of profound study under masters, from what you repeat of their information. If you insist on sticking to their misinformation as true, then do not promulgate it as Judaism.