My guest room has a cheap 40inch TV the audio is terrible compared to the visual output. And I can play what feels like cinema quality 7.1 audio and 4K video over it. The result is the audio is terrible, tiny distorted. Muddy. Hard to understand if it's anything other than a voice over.
In 2005 the quality of whatever I was watching was crap but it was mixed knowing that it was likely going to be viewed that way!
That's been my conclusion admittedly based on not much.
Older TV shows (and many movies) were done more as closed set stage shows... often more emphasis on understanding what is said was made than making sure the feel/drama was best expressed.
I find myself turning on captions a lot these days... it definitely detracts from the viewing experience, but not as much as having to crank the volume to crazy levels.
Unless this is something they just wrapped up right now and going forward we'll have better mixes for common media playback devices. Most people use stereo thinny speakers on old laptopts, and subpar phones.
I think we can overcome this with better listening and playback options though... personally, I just turn on captions/subs where available.