The ones under the Baltic (with the exception of some islands) are not 'critical', as in they're used for reasons (cost, latency, directness), but those reasons are not b/c there's no other way to connect to the Internet.
But cutting a few of them doesn’t mean the transactions don’t happen, they’re just slightly delayed, so you can’t count the full value of those transactions as a loss.
To adapt the old saying, the internet interprets cut cables as unreachable intermediate nodes and routes around them.
So, annoyance at most.