The Plain English Campaign with their Crystal Mark accreditation deserves much credit here too. They've been successfully removing jargon and 200 word convoluted sentences from business and governments since the 70s.
The global financial crisis has a lot to do with it. A ton of the best talent in London were at startups and design agencies which went under; a lot of them went to the Government and did a really rigorous job; even though they've now moved on, the culture they put in place was bulletproof.
Yes, in recent years many top GDS employees have left[0].
Most common past 'companies' for GDS employees on LinkedIn are Department for Work and Pensions, Cabinet Office, Ministry of Justice & Home Office[1]. All the people I know of there used to work at the BBC.
I agree we should aim for good vocabulary and English, but we can't forget many who have English as second or third language, or were unable to get quite the same level of English from school.
When it's a statute or legal judgement I'm happy to see the necessary precision in terminology. When it's a passport application, or an electric bill I'll take the simplest terminology viable. So I can spent the least time skimming it and still get the right information. Much like writing for the web. :)
I don't regret the death of overly flowery Victorian formal business writing. Notwithstanding your views heretofore. :)
The average reading age in the UK is 9 years old. Are you proposing that the Gov.uk website be inaccessible to the population it serves?
Don't forget, unlike other websites and apps, people do not use Gov.uk of their free will. They are forced to use it, in the sense that it is the official source of information and services from the government.
In most cases, it is possible to convey the same information in a concise manner to the average person.
Just like with math, I get the impression that sometimes the level of jargon/legalese used is an attempt to differentiate oneself from the everyday person. The same information could theoretically be put forward in a way which is understandable to all, not just those with a degree.
From experience, the information provided on gov.uk can be incorrect because it is simplified too much. Very important aspects are lost and it becomes misleading.
As the saying goes, simplify as much as possible, but not more.
Although note that there's a non-zero number of professional linguists and grammarians seem to consider Strunk & White to be prescriptivist nonsense that you're better off ignoring.
gov.uk is a fine continuation of that tradition.