I accrue FF points the same way most people do, by using a credit card for all purchases and paying it off each month. I've had a lot of useful flights over the years, especially over longer distances. The days of LCC mean it's often not worth even thinking about it, and there is really only a limited number of scenarios where they are useful. I still manage to use mine though.
Taxes on a return flight Mackay-Melbourne were $100, still better than any available return fare, even if I booked it twelve months in advance. Recently booked a return flight Brisbane to Honolulu for October this year, and was a little surprised to see the total tax costs around $330, but still a good saving over a return flight. The taxes you quote seem exorbitant.
So, of limited use, but not useless is the final analysis I think.