I think the issue is that we haven't yet demonstrated that real, actual equal opportunity won't lead to entire graduating classes of engineers and scientists - we still have the situation where "well Billy had to move schools 13 times because his family kept getting evicted, so while he might have been smart it's the brick pits for him, just look at his grades."
Probably not. Whenever wages go up enough, companies find ways to automate manual jobs.
On Market St in SF, I just walked by a cafe featuring a robot barista. Doesn't somebody have to make my latte? Turns out the answer is no.
Which is why my home town has the one of the highest diversity's in the world compared to its population.
The few "shop" classes we had were usually the ones where they actually got decent grades.
Apprenticeships where never for unskilled low archivers at school for example where I lived in the UK if you left school with poor results you didn't get an apprenticeships with the local engineering firms or the government - you worked in the brick pits for LBC