The point of the disclosure system was that employers seeking to place certain individuals into positions involving access to kids and vulnerable adults would need to have sight of an individual's criminal record in order to make an informed employment decision - hence the exemption to the ROA.
The CRB was never meant to be a 'certificate of good conduct', and is not meant to be a mechanism of shortlisting. The difficulty is that employers and volunteer organisers are best described as 'risk averse', or ruddy mental.
Apart from the obvious ones, an adverse disclosure is not a bar to employment. If an employer cannot accept the risk posed by a 10 year old minor shoplifting matter, then they need to be repeatedly struck with a clue-bat until such time as they come to their senses, and preferably stopped from being in a position where they're responsible for safeguarding children or vulnerable adults.
There are very cogent reasons for a CRB system (Ian Huntley, obvs), but the application of the CRB needs to take place at a point at which the CRB'ee can obtain damages if an employer decides to unreasonably withdraw an offer on the basis of that disclosure.