The statement “universities can’t take everyone” is clearly true. But there is a big jump from that to saying “we should stop people from applying,” for two reasons. Firstly, the more obvious conclusion would be to find a way to increase the number of places available, on the grounds that more students means a larger pool of knowledge to draw from and therefore academia will be better. Secondly, for this to have the desired effect we would need the good people to continue to apply, and this is by no means guaranteed – they may simply waltz off into jobs and be lost to academia, in which case we will actually end up worse off.  The limited number of places is a problem, but the proposed solution may make things worse.