There are booming industries where the boom mostly floats top executive boats, though. Ask an Uber driver, or an Amazon warehouse worker.
[1]: https://steveblank.com/2009/12/21/the-elves-leave-middle-ear...
Now you need the job more then the job needs you; eventually you may find yourself in a position where employers compete to have you in the team instead.
As noted in other comments, this DID check for causation and found employee happiness led the benefits, not the other way around.
Article: "However, the authors cite studies of changes within individual firms and organisations which seem to show that improvements in employee morale precede gains in productivity, rather than the other way round."
A theory could be that employers see the improvement in productivity before they are measureble by the methods employed and therefore are happier. E.g. bad processes are replaced which gives happier employees before the gains are evident.