This opinion appears to contradict the many posts where FIs are looking for opportunities to instruct and simply can't find them! I have heard many debate the pros and cons of doing a FI course, if the perception is that there is little chance of work at the end of it!
It is probably fair to say that there is a shortage of experienced FIs, the younger ones inevitably move on to the airlines whilst the older ones fade away. There are still a number of FI(R)s looking for work.
There are many PPL holders who would like to instruct but, are put off by the CPL or even ATPL exams and associated courses. Perhaps the greatest problem is the lack of a CPL theoretical course, which is not financially viable for training providers. ICAO Annex 1 requires that FIs should demonstrate CPL level knowledge; for many years this was achieved in the UK by passing a FI pre-entry test. JAR-FCL reiterates this ICAO requirement. With a little imagination this requirement could be met by without the need to complete either the JAA CPL written exams or to attend a mandatory course of training!