Of course, but when you get to 700 episodes and 11 movies it's difficult not to label things as canon when the creators and producers have tried to follow that line and have it all set within one universe by claiming things to be within continuity of other series and movies.
Yes, I'm not disputing that. I'm just saying it's important to understand that "canon" is a concept with a lot of ambiguities to it, and it needs to be taken with a grain of salt and not obsessed over the way fans today tend to do.
Bottom line, no matter how much creators may put forth the conceit that it's all one universe, it's not. It's not a "universe" at all because it doesn't exist. It's just stories. Canon is just about categorizing one set of stories versus a different set of stories, but they're all equally imaginary, and definitions of canon can be changed or abandoned at a whim. There is meaning to canon, yes, but its importance should not be blown out of proportion.