I'm not comfortable with this either, but I recognize it's hypocritical-- after all, smartphones have microphones AND camera and are internet-connected running proprietary software.
There's nothing hypocritical about not wanting FURTHER intrusion...
Not to mention, smartphones don't record all you say 24/7 and send it to a foreign data center, except if tampered with. These devices do as their normal operation mode.
Not to be blindingly trustworthy or anything, but I'm pretty sure none of these devices currently state that they send everything you say 24/7 (or more specifically, the Echo). That would, again, only be if it had been tampered with.
The way I see it, the difference is the burden in not having the device. For a lot of people a smart-phone isn't necessary, but it's extremely inconvenient to go without. Whereas these devices are new, so they aren't ingrained into our culture yet.
I agree with you and OP. If there was a good open-source version of either of these, I'd buy them in a heartbeat, but there's not.