But it did fail. It did not lead to the show be created. What happened was it got near totally reworked, new customs, prop changes, major recasting to the point only a single actor and his character remained at all. It failed, it dd not lead to a TV show, this is why its a failed pilot. That is what you call one that does not get made into a TV show. Trying to sugar coat it does not change the fact it failed.
Trill where canon as well, and DS9 rewrote that whole race. Trek retcons cannon when ever it dang well feels like it. How the cage looks is irrelevant, You can keep the events and have it look like discovery with zero impact at all. Who cares they use TOS style phasers and not lasers, who cares they use the delta and not the goofy mission patches no one really likes. None of that has any impact on the events or stories at all.