There seems to be a certain consensual hallucination that happens with these acquisitions. The acquirer says "you're amazing, you do great work, we don't want to change a thing, you'll still be completely autonomous, we'll just help you accelerate". And there's a good reason for it, the employees came to work for Slack, not Salesforce and if they all quit then the acquisition will have been a waste. So Salesforce makes all the same promises, but at the end of the day there's reality. The second Salesforce bought Slack, Slack ceased to exist, and all the workers now work for Salesforce. There's no culture clash between Slack and Salesforce. There's a Slack culture that once existed, and now there's Salesforce culture the company those workers now work at. You can embrace it, you can be unhappy, and you can leave. But remember, you're at Salesforce now and those other 70,000 workers - they joined the Salesforce culture, not the Slack culture and they sure as hell didn't buy you because of your culture.
And all those promises about Slack being independent and autonomous? Well sure, that was the plan, but now Slack is a part of Salesforce and Salesforce makes decisions that make sense for Salesforce, not Slack. So no, you don't get your own sales team, and no, you don't get your own customer support team. You're part of Salesforce now, it doesn't make sense. Oh and no, you aren't going to get the benefits you were getting at Slack, you don't work at Slack, you work at Salesforce, and hey! Some of those benefits may genuinely be better. Those HR reps that sorted all your perks at Slack? They're working in a Salesforce HR department now (if they weren't fired) and they're working to give you the Salesforce benefits.
It's a tough message but when someone buys the company you work for, you no longer work at the old company, you work at the new company, no matter what anyone says.