Canon lines from TOS "Metamorphosis"
KIRK: Zefram Cochrane of Alpha Centuri, the discoverer of the space warp?
COCHRANE: That's right, Captain.
MCCOY: But that's impossible. Zefram Cochrane died a hundred and fifty years ago.
SPOCK: The name of Zefram Cochrane is revered throughout the known galaxy. Planets were named after him. Great universities, cities.
KIRK: Isn't your story a little improbable, Mister Cochrane?
COCHRANE: No, it's true. I was eighty seven years old when I came here.
So, ZC of Alpha Centuri, discoverer of the space warp, revered all over, died 150 years before TOS at the age of 87.
So, he was revered and linked to Alpha Centuri, which must have been where his great, revered, achievement occurred - like Lawrence of Arabia. And surely discovering the thing that made warp drives and subspace radio possible must have been his greatest achievement - unless you can suggest something more amazing??
TOS is considered to be around 2264 to 2269. So ZC "died"(vanished) 150 years earlier around 2115-ish at 87.
First Contact is 2063, so 2115 less 2063 is around 52 years difference.
87 less 52 is 35. James Cromwell was around 55 during filming, so some 20 years difference.
First Contact canon and Metamorphosis canon have ZC's age disagreeing by about 20 years. They disagree on the location of his greatest and most historically revered achievement.
This is just one super obvious example where Star Trek canon is an infinitely mutable mess that makes no sense.
So,I fail to see how the "it's not worth discussing unless its canon" line can ever be an honestly held and valid point for any ST discussion. Ymmv :^)