How can a barrister succeed, if a barrister lacked 'the depth into law'?

Question

From the 3 m 51 s juncture of Lord Neuberger's interview at the Cambridge Union of 2015/12/12:

On the other hand, I do honestly feel, and I am sure some people who read my judgements would agree, that because I didn't have 3 years concentrating on law, I didn't get quite the depth into law that I might have got if I had read law.

Having read Lord Neuberger's biography, I know that he has a BA in Chemistry, but he converted to law via the CPE instead of studying for an undergraduate degree in law.

But I do not understand the bolded above. If he had less 'depth into law', then how did he succeed as a barrister, to be appointed: a QC, then a High Court judge, Court of Appeal judge, Lord of Appeal in Ordinary, Master of the Rolls, and then the President of the UK Supreme Court?
Surely he must have done something right?

Answer 1

The legal system advances practitioners on a number of criteria, not all of which relate to their legal education.

It's essentially the same for all professions - your schooling/education may or may not determine your success in the field. Also relevant would be the social circles you navigate, your achievements post-education, and so on.

Answer 2

If a person wins a race they may say, "I think, and you probably agree, that I could have run faster if I had trained."

That doesn't mean that the winner isn't fast. It doesn't mean that they are not the fastest. It just means they could do even better if...