I don't think there is a perfect answer. You want exams that all can access (ie answer a decent % in).
You want students to be prepared for GCSEs, but you don't want to put the students who are destined for vocational qualifications to go through a system designed to prepare students for GCSEs.
However you don't want to split them off into separate systems
You want understanding, but not to have to specifically remember anything because Google has the answers.
Maybe the solution is the technical/ gymnasium system they have in other European countries. The sats results indicate that testing at 11 does indeed have strong predictive power, but there are exceptions for false positives and false negatives. So the two paths need to allow for movement between them and, crucially, they both need to be respected by the population at large.
Getting that respect was where Cases and before then, secondary moderns feel down. Perversely, however, this policy of sending 50% to university might be what finally breaks down that barrier, because when you see a child scrape into a week course at a bottom of the league tables university, and then you look at another starting out in an apprenticeship, don't you ask yourself whether the child doing the apprenticeship may well be the one who is on the path to greater success?