That's fair.I remember specific innings rather than the no of centuries a batter has.A 70 in really difficult conditions/match situation can be worth more than a ton on a road.I don't disagree that centuries aren't the be all and end all but Root has had ~0 actual impact in Australia. It's not really about whether he can score A Hundred, it's about whether he can actually play a match defining innings in Australia.
However,in general a players average and number of tons and where they got them are a benchmark by which to judge players initially.