Hi why not allow mp4 videos to be uploaded they are small size you could limit them to 10mb for examble
I dont like uploading to youtube so much
I think it would be a bad idea to allow video uploads. The problem as far as I suspect, is, that you can have hidden sites and so use itch as a host for content that is not allowed here. Applications can be scanned for malware. In theory.
Also, a game dev that does has a video promoting their game usually promotes the game not only on itch, so the video already exists elsewhere (does not has to be yt) ... so why bother uploading another copy to itch.
mp4 is a container format and not video. You can have jpeg and png in there. Though this is seldom seen. But a lot of what used to be animated gifs is nowadays a short video, but I see webm used for those. Might be possible with mp4 too, or there are some creator tools that save still images in mp4 container, so it is a format seen more often on the dev side.