You are saying you would kill yourself if you could not see you dead friend on some app? On the contrary it should be easy for a relative to remove a deceased individual from social media, especially so that they are not captured to be zombie-bots liking some far-right posts years they have been gone. Meta doesn’t give a shit about this, but tapping phones would actually solve this problem by itself. If you are not online nor tap phones with anyone for say a year, your account dissappears.
Once this is actually needed, they can add a feature for marking someone as deceased. It could freeze the relationships, disallow new ones, disallow any new content, mark person as dead.