Bitcoin ain't perfect, and you could say that requiring internet connection is one of the downsides.
And yes, theoretically, having the internet shut down woldwide(for whatever reason) could be a problem. Fortunately though, chances of such problem occurring becomes less and less by the daily because of advancing technology. Starlink seems promising, and Blockstream satellite already exists. And if Bitcoin adoption just continues to go up from here, expect new technologies to be created to decrease the chances of downtime in the future.
Still It's interesting to consider whether bitcoin really is comparable to gold in this sense - if the world really goes to shit btc aint helping noone. COVID showed us how fragile civilisation is it wouldn't take much...
It would take A LOT more than something like a COVID pandemic to take down access to internet worldwide.
It's true that bitcoin's weakness is only found in the internet connection. Maybe if today's internet connection isn't as stable as it used to be, bitcoin won't have a long future. But thankfully everything has been resolved a bit. People are increasingly honing their skills in this regard.