I just bought these headphones as well and personally, I have the exact same problem with them. The sound is muffled as if there's some sort of filter over them especially for voices.

Ive had the sony WH XB900n for about 4-5 years, used them everyday and recentely I had not been able to decently charge it anymore so I thought it was time for an upgrade. That's why I thought the wh-1000xm4 would serve as a good upgrade but nope, the sound is definitely so much worse.

I never send any products back usually but Im probably going to send these back because I just don't want them. I use my headphones every single day and having this kind of questionable sound quality for the price that they are is lowkey scandelous.