“MO was invented by RYBS around a half-century ago while the Torah was given to us thousands of years ago.”
The term perhaps, and some of the specifics responding to our current environment. But the shitta of learning secular studies and participating in general society is certainly traditional Judaism as our ancestors practiced it. Primary example would of course be the Rambam. Haredi Judaism is a modern day invention to respond to a more open world. Certainly legitimate but hardly traditional Torah Jewry. Ill give you another example…the GRA as is well known translated several geometry books…not a specific isolated example im just demonstrating that what we call MO is more closely aligned with how Judaism has traditionally been practiced.