Did not know that. The MCU seems like they had some sort of roadmap at the very least. Nobody has ever pulled off a decade’s worth of interconnected films before.
There’s a general roadmap, yes, but it’s extremely modular/flexible from everything we’ve seen. Thanos wasn’t even considered as a major villain until after Whedon decided to put him in the Avengers 1 credits scene as a nod to comic fans.