https://www.gamespot.com/articles/pokemon-go-dev-will-fix-ex-raid-battles/1100-6454382/

Following several weeks of field-testing, Pokemon Go developer Niantic will be making some changes to the game's upcoming EX Raids. In a post on Twitter today, the developer announced it will adjust the feature before it rolls out globally.

According to the tweet, Niantic will specifically "work to improve the invitation system based on what we heard from you." Unlike a typical Raid Battle, EX Raids are invite-only, meaning players need to receive an invitation in order to participate in one. However, feedback from those who've tested the feature has been negative due to the seemingly random nature with which invitations are distributed.