Let's recap then:
If a prophet speaks in the name of another god, he's a false prophet. This is mostly irrelevant for the discussion.
If a prophet speaks in the name of Jehovah but his prophecy does not come true, then he is a false prophet.
False prophets are to be executed.
No exception is being made for far-future prophecies that are supposed to be fulfilled long after the prophet's death.
From all of the undisputed facts above, I infer that there was a common expectation that prophecies be fulfilled within the lifetime of the prophet (because otherwise false prophets could elude execution by claiming that their prophecy will not be fulfilled for 500+ years).
Therefore, all of the prophecies supposedly about Jesus Christ are bogus.