Using that logic however means that the first Iron Man isn't cannon. TIH was released almost a month after the first Iron Man, meaning that would be a marvel film made after the MCU was started.
It was going to be cannon, was released as cannon, but when it was shown to not be accepted by the people, was scrapped as cannon, wiped up, thrown out, and was to be forgotten. Marvel wanted it to be canon, but after it's release, and the Hulk reboot of the Avengers, it is to be considered a movie which failed to be accepted well enough to be cannon. Whether it really was that bad or not, I don't know, I haven't seen it, but obviously marvel saw it wasn't accepted well and removed it from cannon. Simple as that. From what I have seen it doesn't look great, the actor doesn't seem great either.