I believe you are confusing the philosophy of Relativism and the physics of Einstein's Relativity. Einstein’s relativity is not relativism. Quite the contrary: relativity is founded on a principle which is not compatible with relativism.
The main difference is that relativity is the state of being relative to something else while relativism is (philosophy) the theory, especially in ethics or aesthetics, that conceptions of truth and moral values are not absolute but are relative to the persons or groups holding them. (see: https://plato.stanford.edu/entries/relativism/#:~:text=Relativism%2C%20roughly%20put%2C%20is%20the%20view%20that%20truth,confined%20to%20the%20context%20giving%20rise%20to%20them.)
So with respect to physics, "relative" refers to relative motions between objects. It's not that "everything is relative". Time intervals and position are not absolute, but relative to the velocity (Time Dilation and Length Contraction). The term is well-defined and unambiguous. The philosophy of relativism and real world physics of relativity are two separate unrelated concepts.
Albert Einstein originally was going to call it it a 'Theory of Invariance': https://www.asa3.org/ASA/education/views/invariance.htm#:~:text=The%20%20%20%20%20reason%20is%20that,became%20%22everything%20%20%20%20%20is%20relative.%22
I am a huge fan of Sir Isaac Newton, his contributions to various fields and his passion for exploring areas that others would not even have bothered with are inspirational. He gave us things that contributed to math and physics that otherwise would have gone unexplored. And his theories still work well for majority of things. But they do breakdown for other areas, which Einstein solved.
This video of a real life example of a Muon from the Special Relativity Course provided by Stanford University o the Coursera MOOC Platform is an excellent illustration:
https://www.coursera.org/lecture/einstein-relativity/a-real-life-example-the-muon-M5Koo
These links may provide more context to the debate and also real world examples of Special Relativity:
https://www.ligonier.org/learn/articles/relativity-relativism-and-modern-age
https://www.livescience.com/58245-theory-of-relativity-in-real-life.html
https://inside.mines.edu/~tohno/teaching/PH505_2011/Adam_RelativityStory.pdf
https://physicscentral.com/explore/writers/will.cfm
https://www.sciencenewsforstudents.org/article/einstein-taught-us-its-all-relative
https://www.sciencealert.com/watch-the-famous-twin-paradox-of-special-relativity-explained
N.b. I am not trying to take anything away from your proposal or antagonise you. I believe it is always good to have healthy dialogue and if you have anything you would like me to look at, theories or concepts which I may have missed- I welcome your suggestions. I am happy to change my point of view if concrete evidence based reasoning is provided which demonstrates a gap in my knowledge and shifts my perspective. I would thank you for it.
