I definitely agree. As an owner of all three lenses, they address different markets. Yes, they overlap, but the 100-500 is versatile, take everywhere lens, while the Sony due to its bulk is a more intentional outdoors/wildlife lens. The Nikon being a prime has--not surprisingly--the best IQ in the 500-600mm range but is less versatile being a prime. All three are excellent optics, nonetheless, there is room for a lower-priced Canon zoom to compete with the Sony. Having the 100-500 I would not be a buyer unless it went to 750 or 800mm and was truly excellent at its long end. Anything shorter would just duplicate what I already have.Comparing pears and apples...
RF 100-500mm is a five times zoom, Sonys 200-600mm is a three times zoom. The RF is much versatile and compared to the Sony very compact. Both lenses aim at different customers, so a comparison makes absolutely no sense...
I hope/ wish that Canon will release another telephoto lense in the range of Sonys... in order to distinguish from the RF 100-500 I guess it should be about 200-600/ 700 or even 800mm. Since neither of the 70-200 take any converters I'd guess there is a need for a truly dedicated telephoto. A 250-750mm three times zoom would be nice imho.