In your opinion, what are the benefits of adhering to canon? What creative potential exists in jumping off from it? Where has Star Trek (or other similar franchises) done it well or poorly?
Canon is always a difficult subject. On the one hand, canon is a great starting point for stories, as locations, events in the timeline characters are all already established and stories will be told by the world that has been created before, and you do not have to reestablish the rules of the universe.
On the other hand – if you then depart or break the rules of the universe because you did not care/ did not know about the rules can ruin the entire series.
In addition, some stories should not be told. Mostly these are things that are already established facts in the existing universe. Prequels are uninteresting, as everybody knows what will happen. (the series Enterprise -> The Federation is created, Star Wars Rogue One -> They steal the plans). In the imagination, these events are more interesting than actually telling these stories in detail.
Stories benefiting from Canon
A great example of this is the Battle of Wolf 359, this first devastating encounter, changed the Federation. It became more militarized and for the first-time warships like the Defiant were proposed and build. – As a result, the federation was prepared for the war with the dominion and when the Borg eventually returned. The entire universe changed after this event.
Many stories of Deep Space Nine looked at the long term consequences of previous stories of other Star Trek Series. For example, they revisited the Mirror Universe. In this universe everything was reversed, however, Kirk persuaded the “evil” Spock to stop the brutal conquests of the Human Empire. – When Kira visits the Mirror Universe, the humans actually followed Kirks advice, however as a consequence the Human race has been enslaved by the Klingon/Cardassian Empire. These stories would not have been possible if the series would not adhere to canon. (While at the same time the mirror universe concept, was used to overcome the limitations of the core canon)
Breaking Canon, Breaking the series
In star trek discovery, Klingons are religious extremists, Vulcans “fire first” and the Federation is displayed as a military crew first then explorers. – these are all instances of radical departures from the star trek canon. Making long time fans asking the question if this is still star trek or not.
Other famous examples happened in “Star Wars: The Last Jedi” – There are so many instances of breaking canon that it is questionable if it is actually a star wars movie. Luke Skywalker wanted to kill a person in cold blood, where when looking back at the Return of the Jedi, he believed in the good in even the personification of evil (Darth Vader) and he was even successful to turn him to the good side.
It introduces Light Speed Ramming – a technique that effectively eliminates the need for Death stars, as you can just shoot a Starship with lightspeed into anything and it will be destroyed. You do not need to build an expensive starship anymore.
Viewers will stay with the series if the stories are part of the canon. The extended star wars universe was a great way of continuing the stories of star wars. TNG, DS9, and VOY were all part of one great story.
Enterprise looked at a time period that did not matter to most people, they wanted to know how the original canon was going to be continued. Discovery looked at a time period that did not matter and broke with the core canon of star trek. Thus long-term fans abandoned the series.