"I don't agree that those 74% are written off"
How many 11+ failures have you spoken to? I know for a fact that just about all of the people I know who failed the 11+ felt 'written off' at 11. I took my 11+, so was among a whole bunch of children and sibling who also did, so I know these people.
We, in the UK, live in a society that valued academic attainment over just about everything else. On MN, we use the word 'good' as in 'good school' to mean one with great exam results. We are not interested in our engineers, our makers, our manufacturers, We are in awe of good academic results (which is one reason why we allowed so many high academically attaining twats in red braces to destroy our economy- I mean hell, they had firsts, didn't they? Who cares what in? The banks swept them up! We believed them!)- so, no, we don't value vocational. So if you fail an exam allegedly designed to literally sift the clever sheep from the dumb goats, if you fail, you're a goat.
You can cite 'focused selective education' all you like, but here in the UK, in selective areas, we only provide that for the academic.
If we did things to redress that: How would you feel if SM teachers were suddenly going to be paid 25% more than GS teachers in that they have a harder job, having to differentiate between Child 73 and child 20? (Using the '1-23%' in GS model)? How would you feel if all incoming funds were diverted to fantastic tech facilities at the SM? To endless research into getting the best out of a less academically able, diverse cohort? To glittering prize-givings? And graduating DC getting jobs earning at least as much as your DC?
I'd guess you'd not be happy.