> SS through ML is commonly a nasty, duct-taped work-flow that at best results in a system that looks more like a POC or DEMO than a proper production system, unless you work at Bing/Google that is (probably, but I have no hands-on experience of those systems).

This is being worked on in Solr community. See an in-progress book: https://www.manning.com/books/ai-powered-search And related issue for an example of work: https://issues.apache.org/jira/browse/SOLR-9418