I went to the referenced article about the 15 years (https://eprints.kingston.ac.uk/id/eprint/42134/), but I'm very skeptical as to what that actually means without more info (I just read the abstract, don't have access to the full article). I'm sure a huge part of that is there is much more M&A than there was 80 years ago. I also don't even understand how the quote in the abstract can make sense, because it states "The average lifespan of a US S&P 500 company has fallen by 80% in the last 80 years", but that article was written in 2018 and the S&P 500 was only created in 1957. There were no "S&P 500 companies" 80 years ago.
I'm also guessing the WEF's survey list skews heavily, if not entirely, to large, established employers.
I think you are right about the M&A influence, just looking at one random company sitting at 434th of the S&P500, it has been around for only 16 years and the abstract mentions 5 other companies that had major influence on its trajectory.
I think this is still on point with what the parent was alluding to: if your company lives and dies by M&As, do you have a clear vision of what the future will be in even a few years ? When two company merges, one of the vision mechanically dies after all.
I'm also guessing the WEF's survey list skews heavily, if not entirely, to large, established employers.