Import substition is a process where domestic industry develops by adopting the processes of overseas industries contributing to imports, so that the country can import the raw materials and make the product, instead of importing the full product at the market price. Most surveys of macroeconomics reveal that it is integral and foundational to the development of most industrialised countries today, e.g. China.

The exporter countries contain smart people who may seek to suppress this process to maintain revenue flows. This prevents the development from happening.

Two examples:

1: the 'unequal treaties' between 19th century Japan and America prohibited certain kinds of tariffs and subsidies by Japan. This allowed westerners, prominently Americans, to maintain market share in Japan by product dumping.

2: in 18th and 19th century India various British offices at different times had policies of having their sepoys arrest textile workers and maim them by the forcible amputation of both thumbs, to preserve the market share of British textiles.

Agreed. For a while, importing stuff “on the cheap” looks like a good deal, but overtime if that makes your own industries weak, you are just losing power.

You can't win by just buying stuff from someone else; it appears that people have a hard time understanding that nowadays.

If you can't produce something domestically that takes away the need to import that thing, the nation cannot gain power.