Well, sure. Everything you end up doing in life will open doors that would have otherwise remained firmly closed if you did something else instead.

"Everything you end up doing in life will open doors that would have otherwise remained firmly closed"

Oh no. It is also quite possible to do things, that will very firmly close doors, that were open before, or making sure some doors will never open ..

(quite some doors are also not worth going through)

Of course. In fact, it is widely recognized that in a poor economy PhDs can be in an especially bad economic place as any jobs that are available deem them "overqualified".