I think the "lack of background music" is actually a bug, that it isn't starting correctly.. some games, the music is always there, in others it just never seems to play at all. Every patch makes it either worse or better. Then worse again.
As for immersion.. I think that's really down to individuals, if you lack imagination, you won't get immersed. I have no issues with running around in the game or driving around all the time, in fact, it's only when I start getting tired after maybe 10-12 hours of play that I even use the teleport system via map.
The Sam reminders have never bothered me, I just acknowledge them, sometimes even saying "thankyou sam" to the screen as he reminds me for the millioninth occasion that I can mine somewhere.. really those prompts should be changed, so when you enter a mineable area for the first time.. you get the notification and then never play thereafter.
But the conversation exchanges between passengers in the nomad or in the field during quiet moments, much of which is regarding your current plot situation are really immersive and when the music does play, it really does transport you into the world of mass effect.
I think it's sad that so many people are saying things like the game sucks, there's no story, no background.. when it simply isn't true, everything is there, you just need to wait for it or look for it. Fact of life that people will hate a game, just because they're hateful people. And that others will just lie, because they're liars.
People and editors etc have made a meal of ME:A out of fairly minor details, giving an unfair judgement on the game overall. There's certainly issues in the game both in physical gameplay and in the mechanics, but overall, ME:A is an amazing and excellent game. One which has me replaying it over and over, revisiting old areas, that sometimes feel like it's been years since I was last there, when in fact it was only a day or so before.
Although I do have issues with some lacking aspects of the games mechanics, I still give Mass Effect : Andromeda 11/10. It will always be, one of my favourite games of all time, just like ME 1 & 2. 3 not so much.