I don't see why the 5D II isn't reactive enough. I think it is a matter of getting to know it well enough, and anticipate if possible.
This was with 5D II, 100-400L at 400 and F5/6, in miserable light. Slightly cropped (about 5 % on two sides).
And yes, another camera would probably make it easier. However, from a view finder POV it either is a FF camera, or a 1D series camera, how heavy it may be. I find that the 7D has the worst tunnel vision of all Canon cameras, and I can't actually see the whole frame in one go either, which makes it worse for me. Note however that I am a spectacle wearer who can't do without his spectacles.
Kind regards, Wim
This was with 5D II, 100-400L at 400 and F5/6, in miserable light. Slightly cropped (about 5 % on two sides).
And yes, another camera would probably make it easier. However, from a view finder POV it either is a FF camera, or a 1D series camera, how heavy it may be. I find that the 7D has the worst tunnel vision of all Canon cameras, and I can't actually see the whole frame in one go either, which makes it worse for me. Note however that I am a spectacle wearer who can't do without his spectacles.
Kind regards, Wim
Gear: Canon EOS R with 3 primes and 2 zooms, 4 EF-R adapters, Canon EOS 5 (analog), 9 Canon EF primes, a lone Canon EF zoom, 2 extenders, 2 converters, tubes; Olympus OM-D 1 Mk II & Pen F with 12 primes, 6 zooms, and 3 Metabones EF-MFT adapters ....