Earlier quoted context omitted.
A response to your edit, I was on a zoom call with current musical editors / producers and that is 100% part of the problem. Many of today's actors /actresses almost mumble their lines and make it absolute hell for the audio people to pick them up, whereas theatre trained individuals were loud and enunciate the crap out of everything.
They are trying to be authentic. That is what actors are taught these days, to portray "realistic" characters that move and sound as realworld people. The net result is mumbling and tiny little movements that in turn mandate tight closeups and asmr-like microphone placement. Try that on a stage or in any live performance and you will be called wooden. Compare actors like Samuel L Jackson, Percival Ulysses, Jane Lynch…
English is a rather unusual language that the meaning is mostly carried only by consonants, while vowels are almost meaningless.
What actors seem to be doing is that they focus too much on their accent, and the vowels that define it, and mostly ignore the consonants. Which means you can only hear the accents, but not what is being said.