Thanks for the feedback! Right now our recommendation is to integrate Firestore with an external tool for full-text searches. But I agree that this is a workaround, and it'd be better to have an integrated solution.
Adding full-text search natively in Firestore is definitely on the roadmap, but haven't yet found a way to do this in a way that doesn't change Firestore's performance guarantee that searches don't depend on the size of the collection. So far that means we've prioritized releasing other features that we can guarantee performance for, such as the != queries that are coming out this week.