The launcher can only download games whose content is hosted on Itch's servers.
All the games you mention, if you check, must be downloaded from external servers like Mega.
When you access them from your browser, you actually open a page for Mega, Driver, Media Fire, etc., and download from those sites, not from Itch.
As far as I know, there's no way around this problem unless the author uploads the content to Itch's servers instead of external servers.