These are my theories. Of those 'classic' humanities subjects, we'll take English and History as examples, numbers have been exponentially shrinking for years. As long ago as 2013, the TES was publishing articles on topics like why, as a discipline, English was 'not too big to fail'.
There are varying reasons for this. One is that when Blair's target of 50% of the populace being put through university was announced (along with his introduction of the tuition fee), the backsides the HE system put onto seats were largely in the arena of the Humanities and Social Sciences. New disciplines sprung up in areas like Education Studies, for one, which is now shrinking back to its pre-boom proportions. 'Gender Studies' was dying a death - but has now reappeared in a somewhat different incarnation. 'Media Studies' was lampooned as a 'Mickey Mouse' degree. Sociology was deeply unfashionable and departments were closing.
The growth in the noughties was unnatural - this was the UKHE equivalent of the boom and bust cycle. That was the boom. Now we are seeing the bust as things shrink back to where they were. STEM suffered at the time because it takes up a lot more real estate and is very expensive to teach. At that time, around 2005, I counted only six UK HE institutions who offered Chemistry (the most expensive and difficult to risk-assess of the lot). Only two universities offered Marine Biology and a further three or four Geology. That was it.
So what happens? You end up with a surfeit of Humanities jobs, more competition for what's out there, and as supply and demand dictates, what is out there is of lesser value. Meanwhile, STEM was struggling. So governments intervened and started telling students the other Humanities disciplines were 'useless' degrees and that everyone should be studying computer science, medicine or the physical sciences. And so the pendulum shifts.
And now, Philosophy (very unfortunately) is a dying discipline and departments are closing all over the place. The modern foreign languages are taking an enormous hit. History and English have shrunk as disciplines across the entire sector, not specific institutions (although some have been worst affected). Part of this is because of the absolutely soul-destroying, tedious, dismal way these subjects are taught at GCSE and A' Level. And - here's the irony! - now which are the disciplines currently recruiting and earning more kudos? If you guessed AI, computing and MEDIA STUDIES (the horror!) you'd be right, and here also we're experiencing another prime example of how the pendulum often tends to swing back in terms of university disciplines. Suddenly 'Humanities' is a dirty word and people are talking about 'Culture and Media' and 'Creative Industries'.
In summary, we need STEM (and now have plenty of graduates) and we need the arts and Humanities. A thriving, developed society needs both, not a swing from one to the other every two decades. Funding for the arts has been so badly cut that a major opera company has been reduced to using recorded music rather than a live orchestra. The same sort of thing is happening everywhere.
IMO, a culturally impoverished nation is an impoverished nation. With the richness of our country's history, culture, music, arts and literature, I think that would be a tragedy.