70-300mm range gives some space for wildlife photography but on a full frame sensor, it won’t get a close photo of a bird more than 50m away which, in most instances is pretty useless. I use it mostly for travel photos and nature reserves. It’s flexible enough to get some portraits too.
All that said, this lens has the best image stabilisation I’ve come across. You can eliminate camera shake at 300mm even when using a 1/50s shutter. This puts the 1/focal length rule in quite a perspective. The internal components look completely inert to minor hand tremors. Once you start panning, the stabiliser seems to snap to some sort of grid as the image jumps from place to place but as soon as you stop moving, it’s perfectly still again. This does unfortunately mean that the stabilisation is useless for filming