Same thing as the security of the lock on our doors. We know that if somebody really want to get into our homes they will. In the case of IoT and computers add to it the automation of the attack.

What do we do with our homes? Tradeoffs.

We put some valuables in banks, we keep some at home. We insure precious items, if we do have them. We curse when burglars steal from us.

We also install curtains so people outside cannot look at us and at what we are doing at home. There are several level of protections to do the same thing for networks and devices. Of course vulnerabilities mean that they are not perfect. Curtains are not perfect too. Add to that imaging through walls with WiFi or mobile network signals, but that's still fringe at best even if you should read https://news.ycombinator.com/item?id=37469920

So, tradeoffs and be conscious of them.

If that is your choice.

You may also understand that your devices are not secure, take steps to reduce risk, and so on.

Why do you think yubikeys are a useful thing? Or hardware crypto wallets?

Devices that reduce risk, that are designed with the thought that connected computers aren't secure, can never be secure.

Know where risk sits.

I think this discussion mostly comes down to how we interpret the word “secure”. Do we mean “zero risk”, “nothing can go bad”, “no potential attack, ever”?

Or do we mean “low enough risk for this thing , here, now”? I prefer the latter, even if that implies that statements like “this thing is secure” are somewhat useless due to the subjectivity.