What is the word for someone who dabbles in different art forms but can't master any?

Solution 1:

Could the word have been dilettante? It doesn't necessarily imply several different media, but it means a person whose interest in (usually the arts) is only superficial.

Solution 2:

Jack of all trades, master of none.

"Jack of all trades, master of none" is a figure of speech used in reference to a person who has dabbled in many skills, rather than gaining expertise by focusing on one.

. . . When abbreviated as simply "jack of all trades", it is an ambiguous statement; the user's intention is then dependent on context. However when "master of none" is added this is unflattering and sometimes added in jest.