If you open a book of quotations or go to websites like BrainyQuote or Thinkexist you will see thousands of "quotations" which look very similar to my idea of an aphorism. They are all concise and seem to stand by themselves. They come not only from philosophers and writers but from all types of famous and semi-famous people. But, with few exceptions, they were part of a larger book, speech or interview and were not originally intended to be autonomous. These quotes might be called aphorisms but they were not written by aphorists.
I see an "aphorist" as a person who intentionally writes independent, uncategorized aphorisms over a long period of time.