Harsh but ultimately true. I was acquired into Salesforce and my experience matches this. Salesforce is a giant machine and you will be integrated sooner or later. When your big champion, in Slack's case the CEO, leaves you should expect the pace of integration to accelerate rapidly. This isn't the end of the world, Salesforce lets people vest in peace and then leave without hard feelings if they aren't happy with it. Those who want to embrace the Salesforce way are embraced and can have "a Salesforce career". The people who have the hardest time personally are those that try to fight the inevitable and push back against integrating. You can say a lot about Salesforce but people there are generally reasonable and not evil.