David Attenbrough has actually changed the way people think.
Most of the others mentioned are just well known for being on TV a lot
I read that and agreed with it, and then thought about it a bit, and it occurred to me that just the same could be said of Attenborough. However... it is what he has done while on the television, and via it, that marks the enormous difference between him and the irrelevances also listed.
It would seem probable that a majority of the British population - and many more abroad - have gained knowledge and understanding of, and sympathy for the Natural World solely due to David Attenborough's efforts. A very great man.
He is now in his nineties, there are no obvious candidates to continue his work.