I m so sick of this issue every time I play a movie on my android tv i cant hear any dialogues properly until they talking lound or shouting but the sound effects is too high it makes dialogues more unhearable no matter which player i m using Vlc, MX player, mpv they just have Equalizer setting which dosent help at all. I Even tried it on home theatre but same thing was happening it it also
Try kodi, you can raise center speaker volume with it and it should help.
Not sure why you also have issues with your home theater unless it's sound bar or HTiB