[4ad]

I have the same problem. As an additional data point, I have no problem hearing the dialog in documentaries, youtube shows, "casual" TV shows, etc, but I am having a very hard time understanding the dialog in movies and more serious TV shows.

[frompdx]

It seems like around 2000 dialogue in movies and TV shows started to get quieter and quieter while action sequences got louder and louder. It's awful. I am hearing impaired and I watch everything with subtitles, however, I really don't have an issue with intelligibility of dialogue while watching older shows and movies.

[layoutIfNeeded]

That's because older movies were mastered for stereo instead of surround sound. If surround sound is downmixed to stereo, extra care must be taken to compensate for the loss of spatial information, otherwise the dialogs get overwhelmed by the sound effects from the surround channels.