Why was joining WTO such a major step for china?

China joined the WTO in order to be eligible for lower tariff (import tax) rates from the other WTO member countries (most other countries, including all of the industrialized nations). As a non-member, their exports were subject to much higher tariff rates, some of them prohibitive. By joining, it made their exports less costly.

Not all member countries were happy about China's joining, but they felt China's

predatory nature could be more easily controlled by granting WTO membership than by keeping them out.