I see where your coming from, but your saying that I'm allowed to make the video however I want simply isn't true. That all depends on how you interpret the laws around it. Yes, so long as my video follows the conditions set by fair use I should be make the video however I want within those restraints, but that law can be interpreted so many different ways, and the precedence court cases as of so far have sided with the creator of the original content, not with the creator of the derivative work, meaning that even if my video technically fell into fair use, the developer could still have it taken down if they want because it's their game. It is because of this that I still contact the developer of every game before I use it to be sure.
Also, yes I agree that it makes a lot more sense to contact developers external to itch. I'm saying this should be a thing anyway because of the developers that don't have a twitter, or email, or any form of contact within their profile, making it impossible to reach them.