> At what point do we just give up with side-channel attacks on consumer devices and assume the mentality that all consumer devices connected to the internet should be treated as insecure by default.

There is always an endless stream of vulnerabilities for every piece of tech you use: software, OS, router, etc. This fact is not a good reason to embrace security nihilism, for consumer devices, routers, or servers. When any vulnerability is found, it should be remediated within reason (likelihood of exploitation, severity of exploit) and life should go on until the next one is found. That's one of the persistent costs of using technology.