The debt that graduates have is not debt in the sense of a mortgage or loan, in that it is written off after a time, and is only paid when they earn over a certain amount. The amount they borrow is irrelevant, therefore.
As for the increased pool of graduates, this only matters if you think that the 'point' of an education is to put graduates into an elite group who can pick and choose jobs. If you believe in a meritocratic system, it wouldn't matter if 100% of young people had the advantage of a University education, as the best jobs would go to the best candidates.
When I was a student, fewer than 10% of people had a degree, and the number from less well-off backgrounds was significantly lower than that. Having a degree did mean that a lot more doors were opened, and graduates were much more likely to be in management roles. Great for them, of course, but the flip side was that 90% of people (and more than that for working class people) were automatically denied those chances, or had to begin the long slog through day release or evening classes whilst working and often bringing up a family.
A lot of the complaints about the devaluing of degrees (and yes, they are not a guarantee of status in the way they once were) comes from a hankering after those days.
Personally, I would rather we had a system that encouraged equality of opportunity, and gave everyone a chance to have a fulfilling career, rather than one that by definition denied that opportunity to the vast majority.