To answer your third point. Indeed, each solution has its own positioning, which implies requirements and trade-offs. I don't know the positioning of Typesense and Quickwit so I would have difficulty speaking on their behalf. But I have the impression that Quickwit is the new Elasticsearch. In the long term, they will surely position themselves in front of them, put themselves on the log market, and why not of the security analysis. It is impossible to update or delete data makes me think of this. A system capable of managing terabytes of data with precise and fast tasks. Even if it is far from the need of instant search.
On our side, we have a clear focus on user-facing search. All searches can improve the user experience and increase user satisfaction and product retention. Use cases today are mainly E-commerce, marketplace, site-search, media, SaaS application, B2C applications. The needs for these use cases are the same. Search in a fixed data type with incredible relevance and performance.
Moreover, I want to underline this because I see that you mention it in your comments. At Meilisearch, we have made it a point of honor to offer a solution with the best possible developer experience. Everything we do (API, SDK, Documentation), we do it with developer experience in mind.