Is it? I've found that all open core projects I've used over time gradually lock more and more features away with each update and usually end up being more expensive than the closed source alternative.
The latest example is RocketChat which a year ago had a couple of features and one or two gentle reminders to upgrade to enterprise, but now it's getting really naggy. And when I did contact them for enterprise pricing, which is not clearly available, it ended up being way more than we could pay and a lot more than Slack (can't remember exactly now but something like $10/user if we included the bridges to WhatsApp and Messenger).
Can you give any counterexamples of popular, growing open core projects that don't lock away more features over time?