I suspect (and this is not based on any real information) that those instructors who say they can't find work are being too picky in where they want to work - maybe they don't want to move house, and are only looking for work at one or two airfields near their home.
If you are happy to re-locate to where the work is, I think there is plenty of work out there for new FIs, and definitely for experienced FIs.
FFF
-------------