"One size fits all" is a description for a product that would fit in all instances. The term has been extended to mean one style or procedure would fit in all related applications. It is an alternative for "Not everyone fits the mold ". It has been in use for over 5 decades. There are both positive and negative uses of the phrase.
One size fits all Wikipedia
The term "one size fits all" has been used as a common, cliche phrase for over 5 decades. It was already a popular term, in 1975, when Frank Zappa recorded the album One Size Fits All.
There are several positive views of the phrase "one size fits for all":
A wristwatch could be considered as fitting all people.
In women's clothing, a flexible or open garment can be labeled as one-size-fits-all; however, the size is typically a medium size (able to expand), rather than actually fitting petite or extra-large (XL) sizes.
A neck chain could be designed to be worn by men or women.
Bicycle helmets with ring fit systems allow for a single size, also known as universal fit.
In military gear, some items have just one size (but smaller or larger people have already been excluded from military service).
Many baseball hats available for commercial purchase are labeled "one-size-fits-all"
There are many negative views of the phrase "one size fits all" including:
Many customers prefer to have custom-tailored clothing.
Men's dress suits typically have specific sizes for chest & waist measurements.
Shoes are an example where sizes (and widths) vary depending on the specific person.
For the U.S. GI Bill in education, options and coverage will vary depending on each person.
Politically, the phrase has come to mean that methods of administration or political beliefs in one country should not necessarily be applied to another.