Hardly essential. IMO the question ought to be how to select for what Oxford (or any university) is seeking. In the case of Oxford, as I understand it, that is some combination of very high ability and the potential to thrive under the teaching and learning system, including the tutorial system.
Some who are very highly able may not be suited to the tutorial system and that’s fine. Others may feel they Oxbridge is wrong for philosophical reasons - leave them to it.
Problems occur when those who could thrive and best succeed are put off by myth, stereotype or the burden of an extra set of entrance exams at a very busy time. If you are running the household while your single parent works, if you have no private study space, no reliable transport, etc, (if your family is homeless!), then every step of the university application process is more burdensome than those from other kinds of households can imagine.
Removing the burden of an extra step is then a move towards equity.
I would never suggest that Oxbridge is essential to an academic career, but this hardly negates the principle that both real and perceived barriers to application from some of the best and brightest should be removed.
I think intentions at both Oxford and Cambridge are largely good now. But the barriers are multifactorial with many causes beyond the reach of the universities.
I am very glad to hear about @GoodLuckBabe ‘s DS - congratulations to him!
I had not heard that STEP is the best predictor of degree class, @Needmoresleep , but this would make sense. It is by far the most cognitively challenging of the maths entrance exams and assesses a nice combination of cleverness and knowledge. The problems require a level of synthesis not seen in the other Maths admissions exams.
This is an interesting thread.