I have subtitles enabled by default. I don't know whether to place the blame on the acoustics of my room, the mixing of the source, or my hardware... but _I jus

I have subtitles enabled by default. I don't know whether to place the blame on the acoustics of my room, the mixing of the source, or my hardware... but _I just can't hear the dialogue_. My setup is wildly unmatched in that I have a cheap Yamaha RX-V683BL AV receiver (which needs to be replaced, but high cost of HDMI 2.1 makes this hard) and a 5.0 arrangement with two KEF LS50's serving as L/R and one more LS50 serving as the center. Now certainly the receiver and speakers should be paired better. However, even if I'm not driving them correctly my setup is magnitudes better quality than the average soundbar I see most people buying up. Most of the stuff I'm watching is Blu-ray so the quality of the source isn't to blame here. So the question remains, is my equipment that poorly matched, is the mixing terrible, or do I just have hearing loss in the vocal frequency range?