Even that "dumb" (I.e. not a smartphone) little flip phone probably has Bluetooth capability and is vulnerable and is most likely never going to be upgraded to not be vulnerable. It's also unlikely for you to be able to turn its Bluetooth off. It could become infected but not affected, as it's not a smartphone, but perhaps it could possibly become a carrier, and perhaps infect your car or other Bluetooth devices you may encounter. This is all highly speculative and highly unlikely to happen, just possible.
I checked and I actually can turn off the bluetooth on my phone.
So I did.
I don’t connect it to anything but my car anyway and I don’t always use it even then so it’s not an issue.