According to this article, there's more to developing into a strong military power than just having a larger economy: https://medium.com/war-is-boring/8a12e8ef7edc

TL;DR:

- Much of the military might that Beijing buys every year gets directed inward and never projects externally.

- Even after decades of expensive rearmament, China is a paper dragon.

- The same demographic wave that has gifted China with an abundance of labor will soon also transform the country into the world’s biggest retirement home.

Edited: Added a few key points.