Tíreolaíocht is a feminine noun so it should be ní úsáidtear í. Additionally since the sentence is talking about the discipline of geography in general I think an tíreolaíocht with the definite article would be more appropriate.
Both of these are the questions I was going to ask.
Why is it not "an tíreolaíocht" - when Paul was studying chemistry and physics it was "an cheimic" and "an fhisic"?
Should it not be "ní úsáidtear í" – on account of "tíreolaíocht" being a feminine noun?
This is not a copula construction because it's discussing a descriptive quality (important)? If it were "geography is not a school subject," e.g., would it be "ní (school subject) é tíreolaíocht?"
Yes, on both accounts.
Aontaim leis an frása- ' ní úsáidtear í.!