Much more of the post-1927 content was preserved (more of it was preserved with sound once we switched to sound on film) - I'd note however that Silent Movies are virtually unrecognizable by modern viewers as being even the same art form as sound pictures - and sound movies didnt reach the same... production values? as the silents until 1936-37.
The period between 1927-and 1937 was a period of reinvention and learning of a new medium, which is why - my general take is the golden age of Hollywood was 1939 to 1959.
Consider what films came out in 1939 -
* Gone with the Wind
* Wizard of Oz
* Mr. Smith goes to Washington
These are films that still find audiences today, now - 80 years or so on.
Most Americans might have seen one movie produced between 1927 and 1938 - but most people who are above 30 have seen at least two those three movies at least once.
And that trend continues from there on - where 1940 to 1959, most americans have seen one movie released in each of those years.
So while I dont disagree that we are losing heritage in these things - I take issue with their definition of Golden Age and the idea that there is value in saving everything ever written or filmed.
Much of it wasnt meant to be relevant for decades, it was meant to be ephemeral topical entertainment, and functionally intended to be disposable. Most of the production of Poverty Row, and B pictures by the majors are like this, they were intended for Block Booking, and largely just as a way to fill the content needs of the theaters and as a way to provide steady revenue in the event an A picture flopped.