For Tenet specifically, lots of dialogue without masks was still nearly inaudible on my home theater, while gunplay was deafening. It's not a mask issue, or at least not exclusively - it's an audio mix issue. There are scenes with just two unmasked people that were inaudible to me without having the background sounds painfully loud.
What you describe is infuriating. Many shows suffer from the same issue that even background noise obscures dialogue of main characters that is crucial for the story. It got so prevalent and so annoying that I started to vote with my feet.
If in the first few minutes I have problems hearing the dialogue, I just stop watching, leave a 1-star review with a comment that the audio is incomprehensible and ask for a refund in case I paid for watching. Hopefully, the others would start doing the same and the trend will go away.
I had the same problem. A fairly high end 5.1 system and I was unable to hear most of the dialogue. I have no idea what was going on in that movie, but I could hear the firing pin hit the primer in crystal clarity.
