Using a voice assistant like Alexa isn't like wiretapping your home. It's introducing a powerful vector and risk for easily wiretapping your home, to be sure, but your phone is a vector for wiretapping your room (and your vicinity wherever you go), as is your laptop or desktop if they have microphones that aren't hardware disabled, as is your smart TV or remote if you have one. It's not effectively wiretapping your home, it's effectively making your home wiretappable, which isn't great but isn't the same thing.

It's all about the risk profile you're willing to accept. I personally have much more private information accessible through my phone, computer, and certain cloud accounts than I do from things I'm saying in my home, and I believe a malicious actor (potentially including a large corporation like Amazon or Google) would have a much easier time and/or would be much more likely to engage in tapping one of those sources than a voice assistant in my home.

It's certainly very possible - there was a recent story about how a malicious Alexa skill, if downloaded and installed, could siphon your entire voice history - but those sorts of risks also exist for almost any internet-connected device you own.

So, in my opinion and going by my own risk profile, those people responding "my phone's already compromised" are behaving rationally.