The oversight of medicine has continued to be strengthened such that nowadays it is almost impossible to get in on forged documents. This famous case of a Kiwi psychiatrist occurred due to a loophole relating to Australasian qualifications being recognised in the UK. Closed in 2003.....and that is the point - the system has become more robust. Just a couple of years ago responsible officers started cross checking doctors - a bit like line captains checking every check ride with previous employers. The CAA likewise has tightened its systems.
As others have said issues occur with lax or absent checks in countries where honor is more important than truth, where some applicants are more important than others, and where everything has a price.