Ontario passenger service is down because of the economy (duh!). BUR and SNA passenger counts are down too. ONT is not unique.
The LA Times also completely short change LAWA's effort to develop Ontario as a cargo hub (UPS is the largest airline in ONT), and the fact that ONT has high operating cost because it is a large airport (physical size). It's not like SNA or BUR, which are only a few city blocks long. ONT is a huge and it cost money and lots of people to keep it running.
As to rationalization, IE politicians likes to point fingers but if they really do have a plan to turn ONT into a major international gateway airport, I would like to hear it... The City of Ontario and San Bernadino County have under-invested in transportation infrastructure for years and there is no reason to believe they know what they are doing. Southwest San Bernardino county and northwest Riverside County combined is one of the largest metro area in the US... but it is so lacking in public transportation, the IE ranks 2nd to last in mobility for large metro areas. Does San Bernardino county have a plan to build light rail to link ONT to well... anywhere? Metrolink tracks pass right by ONT and LAWA had asked about Metrolink service before but San Bernardino County did not want to fund it. Bus service in IE is a joke. And for most people, ONT is a long drive away. So why would people in other parts of LA region chose ONT when getting to BUR is so much easier?