Anyone who claims that ISO9000 means they produce a good product is either lying or doesn't understand what ISO9000 means.
Although I agree with your assertion, the misconception comes from the fact the standard is "ISO 9000 - Quality management". The disconnect comes from the assumption that quality == good. The standards where introduced for quality management and to provide a basis to improve product quality. In addition most companies introduced ISO 9001 in the hopes to improve product and service quality. The silver bullet to solve all quality issues. What most missed is the simple fact that you need to do something with all the data you collected and actually improve the production process.