Parallel invention would like a word. Elisha Gray registered a patent for a telephone the same day as Alexander.

It's impossible to fully prove a counterfactual, but few things "wouldn't exist at all" if "that one person" hadn't done it.

Netflix is a decent example. Many people saw the coming of video streaming. We would still be able to stream videos today even if Hastings had stayed at Rational.

Sure, if you extend time horizon to infinity, everything would probably be invented eventually by someone else. Two people filing patents on the same day is an exceptional case though, not the norm.

There are also products that seemingly should exist but don't because no would-be inventor has found capital, eg. a decent bluetooth keyboard+trackpads with the same layout as a laptop. I know because I spent an hour trying to find one yesterday, and they basically just don't exist.