Answer
The answer to the question "Frank Welker has been the only actor to voice Scooby-Doo since 2002" is true. Welker has voiced Scooby-Doo in all Scooby-Doo media since 2002, when he replaced Casey Kasem as the voice of the character. Kasem had voiced Scooby-Doo since the character's debut in 1969.