This is a nice theory, but remember people don't always die in order. If you pass away before your parents, they will almost certainly appreciate your photos. If you die before your spouse, they will need access to documents and will appreciate photos as well.
In a "hit by a bus" scenario, you don't get a chance to migrate things away from your self-hosted solution, and those you leave behind most likely are not exclusively "future gemerations".
I have nextcloud and don't even use it for file management (in that sense). It's a joplin sync server, I use the Cookbook app probably as my most used thing on nextcloud, I use phonetrack, sync tasks.org to it for task management, use the Bookmarks app for keeping track of links.
Plus I never feel bad for running extra services. Idle services use a pretty tiny amount of resources. I had 15 or 20 on a Raspberry Pi 4 before I switched to using an old laptop.