That must be even worse! I connect via Aux, and when the nav voice speaks, it lowers my music. But, because I like to play my music pretty loud, the nav voice sounds super loud and it’s incredibly irritating.
Pre iOS15, I used to like setting the nav voice to “Low”, as this suited me best. I could hear the instructions whilst listening to my music, and the nav voice was unobtrusive. I would sometimes set it to “Loud” if I was driving a more unknown/complicated route, and I didn’t want to miss a turn. I just want that functionality back!
Apple seriously needs to return this feature to Maps. I am hoping that if there are enough posts/complaints about it, Apple will take action.