How should Apple have handled this? Maybe insisted on acquiring the Growl company? I don't think Apple should have just avoided building Notification Center, since that's a big net benefit for everyone.

If an acquisition is rejected/infeasible/not applicable/etc, then I'm not clear on the right thing to do. Acquisition might have been possible with Growl, but for some other cases there's not even a company to acquire. Have any other big platforms done this well?

(Apple's acquisition of Workflow which became Shortcuts seems like a case where they did this well)