Religion is what it replaced. Where one person, with a clique of courtiers who personally relied on him for power, enacted whatever took their fancy. Their word was power, whether it was starting wars or forging alliances with unsavoury countries - and woebetide you if you challenged it.
I think you're conflating religious beliefs with ethics. You can't have a religion that is flexible on beliefs, otherwise it is not a religion, but the actual core religious beliefs are fairly limited. In Christianity, Jesus dying to reconcile the world to God is the whole point; without that it is something else. The whole point of Buddhism is that all emotions are pain, and that realizing that everything really nothing (since all composable things are impermanent and everything is composed) is the path to nirvana. All the other beliefs and ethics come out of this.
But even "submarine" religions (ones that people do not think of as a religion) follow the pattern. Communists worship the State (or perhaps the Party), because the problem with society is the structure of society, so only the State can bring the salvation of equity. American Progressives worship sexual identity. Progressives are flexible--except if you don't accept a particular identity, think that gender is not malleable, refuse to use pronouns, etc.
However, I think even "most religions" are not very flexible. 50% of the world's population are either Christian or Islam, and both are pretty prescriptive in the ethics.
No... I'm afraid you're dividing up a religion in a way that anthropology does not.
You are close to something. You've found the division between worldview, and religion. A worldview is bigger, and is individualistic - but generally founded upon tenants shared by others. "a framework of ideas and beliefs forming a global description through which an individual, group or culture watches and interprets the world and interacts with it as a social reality."
I will say: There is no accepted definition of a religion. There are hotly debated definitions, but no concrete and agreed formation of what it constitutes.
However, generally speaking, a religion is a set of socio-cultural systems, generally tied to a set of beliefs, that tend to have supernatural or spiritual elements. However - the systems are essential, the beliefs are not. [0] Many agnostics and atheists follow religious practices, and form their own religions. There are Christians who do not believe in Christ.
Because the core of a religion is social and cultural, it greatly varies in time and place. The Christianity of Early Rome would be unrecognisable to most Christians today. The religion has changed almost every single practice, over time, because of the cultures that have influenced it today. [1]
[0] An example would be "Jewish Atheism". It is a religion, with practices and rites, but it does not carry with it supernatural or spiritual beliefs. Another would be "Mainline Protestant Buddhism", also known as Secular Buddhism.
[1] An example of one of the most important rites in early Christendom that is no longer regularly practiced in Rome, would be the washing of feet. The host welcomed their guests on their knees, caring for them. Society moved on, shoes and roads changed, it no longer became necessary, and the religion changed around it.
You have one too many negative prefixes there. The Church of England is already established. Those who want to remove that status are proposing disestablishment. Antidisestablishmentarianism is the desire to maintain the status quo.
As someone else pointed out, you're over-negating establishmentarianism.
But it doesn't matter anyway - the UK is a pretty atheist society and getting more so... Those who self-describe as "atheist" in the census:
2001: 15.9%
2011: 25.7%
2021: 37.8%
In Scotland, figures are higher with a majority of the population now describing themselves as atheist (51.1%)
And these figures are only for people who describe themselves as atheists, not just agnostic. The number of people saying they believe "in god" was only 16%, and expanding that to "any god" bumped it to 27%, according to a YouGov poll in 2020.
Also, the most irreligious government ever is the most-recent one, with 40% of MPs opting to make a secular affirmation of service rather than swear a religious oath.
Basically the god-squad is done in the UK, it's just a matter of time - which is odd for a place with an official state religion, as opposed to somewhere like the USA which is officially non-affiliated with any religion, but has "christians" who wouldn't recognise Jesus unless he was white, toting an uzi, and telling them to give him money now to get a great afterlife - "prosperity gospel" my arse.
Religion is what it replaced. Where one person, with a clique of courtiers who personally relied on him for power, enacted whatever took their fancy. Their word was power, whether it was starting wars or forging alliances with unsavoury countries - and woebetide you if you challenged it.