China’s tech world doesn’t believe in the story of David and Goliath.

Startups and investors are abandoning the dream that a smarter, nimbler upstart can topple a gargantuan company. Instead, internet behemoths Alibaba Group Holding Ltd. and Tencent Holdings Ltd., among the world’s biggest companies by market value, use their deep pockets to swallow startups and guard against potential disrupters.

Their...