I think here we are looking into a textbook style definition. But for all practical purposes, military rules Pakistan. It is well understood by its own citizens, especially post-Imran Khan.

>But a lot of countries are terrorist supporting, and the world is happy to negotiate with them.

Would like to understand which countries you mean. No one is negotiating with Iran nowadays. India also was willing to negotiate in the past, not anymore it seems.

Support for terrorism as a state policy is to put pressure without major impact to the aggressor nation. The aggressor is in an advantageous position. Terrorism is low cost high impact (non material, but psychological). There is not much leverage for the suffering country here. So negotiations are not long lasting.