One of those questions where the result varies by the order of magnitude depending on the criteria.
So please don't take the following poor definition like any kind of elitist filter. It's written right off the bat with probably unbalanced numbers. There are very skillful and talented people who work with type but don't fit. Feel free to redefine "requirements".
But let's say (again, for the purpose of this topic only) it would be someone who can produce installable serif or sans typeface, good enough to expect to be sold. Who is familiar with the basic type design tech and theory: contrast, vertical metrics, overshoots, spacing, kerning, basic OT features etc. Someone who can name 20 sans and 20 serif fonts, and who spent at least two working months working on (or learning) type design. If the abstract skill scale is from 0 to 10, then 3 and up count.
This thread gives some insight LINK
. It's posted 7 years ago, and is mainly about the number of fonts, not type designers.
How many users TypeDrawers have?
What is the estimated number of people who have a license for one of the five most popular type design software?