No, your rewrite is not correct. The original message is saying that it is an established fact that watercolor is used by amateurs in painting. Your rewrite is considering reputation as a distinct attribute of watercolor and asserting that only when considering this attribute, it's for amateurs.
Correct rewrites might include:
Watercolor is known for its use by amateurs.
It's a well known fact that amateurs use watercolor.
Amateurs prefer watercolor.
Watercolor is exclusively reserved for use in first grade classrooms.
As someone who paints in other mediums (I dare not refer to myself as an artist), it just goes without saying that anyone remotely serious about the craft doesn't use watercolor. It takes a great deal more skill and work to properly paint in a medium with texture and weight, such as acrylic and then of course oil.
In case you missed it, this is a statement of elitism, which are almost always false and only a reflection of personal preference. Different artists work in different mediums, and just like anywhere in human society where people do things differently, some are going to claim to be better than others.
My answer doesn't quite answer every aspect of your question, I'll leave that open to additional answers.