You are right, industry loads are at an all time high, but load factor doesn't make profits, YIELDS do. Flights are full because many tickets are still deeply discounted, so even though people are filling the chairs, not enough revenues are being produced by those passengers to sell tickets.
By reducing the number of flights, the airlines are shifting the supply curve to the left. Lower supply equals a more scarce resource. Scare resources in turn lead to a higher price for that commodity.
The real question for the airlines is, how far can they cut supply before the subsequent drop in demand (caused by higher prices) negates any benefit of a capacity reduction. That is the real question that has yet to be answered.