If one is actually deaf, then o.k. it's possible to let the BBC or whoever off the hook as far as poor quality sound production is concerned. Otherwise, and for too long, they have a great deal to answer for!
I have Tinnitus, so I appreciate anything which allows me to hear something I'm listening to and interested in without the ever-present white noise!
Think how people used to speak, how clearly they would pronounce words on t.v., how actors would enunciate properly (irrespective of accents). Contrast this with how plays and films often deal with the sound on t.v., now. Would many theatre-goers be able to hear what was being said, if actors just muttered and mumbled and didn't care enough to address the whole auditorium? Sound production is so important.
There is simply no excuse for poor quality sound. For any t.v audiences at home, if you are sharing a play, a documentary, a film or conversation, you will have failed immediately if that audience is struggling to understand what is being said.
Look at the obstacles which so many of us face now, whilst supposedly being entertained, and you certainly don't need to be old or hard of hearing :
Plasma screens with speakers that face in the opposite direction to the screen (often towards the wall!). We often have to find our own way of boosting or supplementing the sound.
Speech no longer dubbed but recorded in a street, for example, along with the action, but often together with traffic/street noise, background 'music'.
Actors often facing away from camera, filming done often in very low light, street light or darkness. No chance of seeing any kind of conversation which all too often involves strong accents, mumbling, words unfinished.
I recall that when the last Poldark was recreated, it seemed that half the country complained about the quality of the filming, the darkness, and the simply terrible sound which meant that even those with acute hearing quite literally lost the plot very early on. The BBC didn't refute the criticism but actually apologised.
Until we are granted sound of real quality with every production, I shall continue to be grateful for subtitles, which also allow me to reduce the volume, watch many foreign language films and documentaries, and - from time to time - allow me to marvel at the incredible/ridiculous words on offer. 😳 (An earlier poster's tale of "Malvolio' appearing in the subtitles as "mild Polio' probably one of the more amusing ones.)