You'll have a smaller base of users that don't want AI slop, but will keep using your AI anyway even if it's there.
But what you lose is the large paying corporate customers that demand 'soup de jour' that end up going to VScode or whatever, and you may never get them back.
Building software is hard, being profitable at it is even harder.
If JetBrains want's to provide a simple plugin for Copilot or Anthropic to keep the vibe coders happy, I'm not going to complain about the feature. It just seems for the past couple years they have been primarily distracted with AI: AI Assistant, Junie, and now agentics.
