Yea, back in film days I had a 500mm f8 Tokina lens that was quite sharp. It was compact enough that no one thought it was a 500mm lens. Once you get over the donut bokeh, one with autofocus would be welcome in my kit. I wish Canon had used a reflex/cat design with the 600 and 800 lenses. They could have been smaller and faster. Those are stuck at f11. I’d rather be stuck at f8.
Oh, please no! At least those 600mm and 800mm lenses have pretty good image quality with nice bokeh. If they were mirror lenses I would just ignore them as the usage is very limited. I don't mind Canon making few mirror lenses but we need affordable high quality telephotos also.