Then you need to change your thinking, f2 - f2.8 is the same as f2.8 - f4, or twice as much light, would you value an f4 zoom the same as an f2.8 zoom? An f2 135mm prime would be smaller lighter and cheaper than a 70-200 f2.8 zoom and let in twice the light thus giving shallower dof and or faster shutter speeds.
I agree that too many people don’t really value the difference and consider the numbers too close, f2 f2.8 does sound too similar! I also agree that for many, despite the tradition of 135mm lenses giving a very complimentary perspective to facial features particularly if the subject has a larger nose, find the focal length a bit long. Though that is countered by the fact that most people use a 70-200 in its place and are often at the 200 end!
Personally I never really bought into the f1.2’s, I just never found a compelling use for the shallow dof, I used to own an FDn 50 1.2L but would far rather have the EF 85 f1.4 than pay so much more for the EF f1.2.