For some of them I kind of lost access so I would need to write emails to instagram or whatever, for others I would need to remember and to access to each one of them and delete them.
The hardest would be gmail with people having my contacts from like 10 years ago…
I would recommend just hiding/removing your content on social media then let it go inactive. There may be some reason in the future you need to utilize the service (looking at you events that are only organized on facebook and restaurants that only post their hours on instagram)