I don't think that's particularly true (red brick and new brick), but if you say so.
Yes, it would be kinder to teach students properly in the first place. But it would also be kinder to be sensible about what errors say about someone's employability.
By the time students get to university, of course they should have learned these basic skills. If they haven't, it would be good if they could pick them up there, and there are usually quite a lot of opportunities to do this, though probably no-one marking essays is going to waste time on extensive teaching of the basics.
The issue is, if someone hasn't learned these basics, do you look for reasons why and excuse them (because sometimes this is appropriate, eg., with dyslexia or a second language)? Or do you say, right, no degree for you.
It'd be silly, IMO, to do the second when these skills aren't that relevant to the degree.
For employers, it is of course more variable: if you need to employ someone with good SPAG, that's fine. If you feel it's an important indicator of someone's ability to be precise, courteous and careful, that's fine too. But I don't see why it indicates a general drop in standards that a few graduates send in badly written CV forms.