So I am interested in this space. There are some alternatives out there but I suspect companies will be concerned with letting a 3rd party have access to the data needed. If you are interested in this space and would be willing to chat with me about what you're looking for OR what you are currently using I'd love to chat! My email is my username at gmail.com
I think neural-network powered search will be the long-term solution for Wiki search specifically, and SaaS search more generally.
Keyword has too many failure cases, and works poorly when there's not a lot of data, or when searching through content authored by others.
I'll contact you offline. Would love to hear more about your experience in this area.