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.

You don't need to project to the heat death of the universe to get Facebook without Zuckerberg.