This is where I feel compelled, once again, to point out that the Marvel Cinematic Universe isn't canon. Neither are the Arrowverse TV shows. Yet people still see those movies and watch those shows in great numbers.
I don't think that's really a good analogy for something like Trek novels/comics, because things like the MCU and the Arrowverse are not telling stories that pretend to take place
within the comics continuity. Rather, they're adaptations inspired by the comics continuity but creating distinct, new universes of their own. And those universes can be said to have their own canons, especially if they have their own tie-in stories that may or may not be in continuity with the main series.
For instance, the Arrowverse wiki lists most of the TV tie-in comic
The Flash: Season Zero as "non-canon" because it came out very early in the series and its versions of certain characters and events were frequently contradicted by the show later on. But the producers reportedly consider things like the
Arrow: Season 2.5 comics and the
Crisis on Infinite Earths bonus tie-in stories to be part of Arrowverse canon since they were written by show staffers, and I think one or two elements of them were even referenced on the show. (The inconsistency with Bronze Tiger dying in
2.5 and being alive later on in the show can be chalked up to Flashpoint rewriting the timeline.) In animation, the tie-in comics to the DC Animated Universe were never part of DCAU canon and were frequently contradicted by later installments therein, but the tie-in comics to
Young Justice are explicitly part of its canon, because they have the same creative team as the show and that team works to make them consistent, even referencing comics events in the show.
After all, "canon" doesn't mean "real" or "true." It's not a value judgment or an official license, just a convenient descriptive term for talking about an overall series of stories in relation to other works derived from it. So there doesn't have to be just one "correct" canon. There can be more than one within the same overall franchise. If an original continuity has an adaptation which is itself a distinct continuity with its own tie-ins, then that gives you two canons in parallel to each other. Or three or four canons, or however many independent continuities there are (e.g. the DCAU,
Young Justice, the Arrowverse, the DCEU, whatever else constitutes a distinct universe with its own tie-ins to classify).
Of course, this doesn't apply to
Star Trek tie-ins, because they aren't an independent universe of their own, just conjectural stories tacked onto the existing ST screen continuity.
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