I think most people would be... just fine? Personally I'm from a culture that is very distrusting of those big platforms anyways, so people are even less likely to rely on them. If my mom lost access to her google account she would be fine, my dad wouldn't notice (he has been using his own e-mail domain forever), neither would my brother (since he makes a new google account with every phone anyways, having forgotten his previous password), and I wouldn't be bothered much either. I've also been doing fine professionally for 15 years and don't even have a LinkedIn account.
It's a similar picture for everyone around me. Some Facebook account or whatever may have seemed important when we were 16, but by and large people grow out of that vain phase, or even grow out of using the likes of Facebook at all. Nowadays whatever can deliver a message will do. There's a dozen ways to each anyone.
If losing access to any one account is a big deal for you, that's more than a major technological literacy failure - it's a basic life planning failure. Do not overly rely on a single thing controlled by people you cannot trust. Even my grandmother would know better.