I love Google voice assistant. My phone's mic is unusually bad though, so if you imagine all of the above with me learning forward and shouting at my phone... ;)
I have the Google Home and my kid loves the Ghostbusters song. For whatever reason if you ask Home to play Ghostbusters you need, first, to specify the song not the movie, even though I have no Netflix integration setup. Then when it gets it correct it will only play the instrumental version for some bizarre reason. Weird, its clear the Home engineers are Ghostbusters fans as you can ask Home "Who you gonna call" and it gives some humorous canned responses, but somehow they can't get playing the Ghostbusters song correct.
Worse, because I have Google Play Music, there's some kind of licensing limit with Home. If I have Home playing music then my desktop PC refuses to play any youtube content, not play music, but unrelated videos. I can't watch any youtube videos unless I log out. Its incredible how bad the usability here. Buying a device for your kitchen shouldn't make all your computers be unable to play videos.
I just called the Skype echo test service to have a listen to what my mic actually outputs. It's pretty bad! The sound is very muffled and almost inaudible unless I cup my hand over the mic and speak clearly. Removing the case doesn't seem to make any difference.
Sony Xperia Z5 Compact, if anybody's wondering which phone not to buy for regular phone calls :) I don't really mind too much as I only make phone calls once in a blue moon, but it would be nice to be able to use voice assistant more.
It seems that with a bit of bad luck, the mic can get clogged up if a drop of water ends up in it.
Try to hold the phone in running water so the mic gets wet, and then carefully blow out the remaining drop of water.