Search is interesting! And it is important to differentiate the web search (Google) and domain-specific search (Solr, Elasticsearch, recent release of http://vespa.ai/). You cannot tune Google to your domain needs and understanding.
For domain-specific search, the basics are there. Even the fancy "basics". It is now very easy to add search to one's stack. In fact, Solr is in so many stacks, it is not even mentioned much anymore. But we still get the contributions back from Cloudera, Bloomberg, Alfresco, etc.
So, the cutting edge in Search is now on personalization, relevancy-tuning, indexing non-text content (music, images, etc), multi-word semantic search, graph traversal and, yes, Machine-Learning. See, for example, https://lucene.apache.org/solr/guide/7_3/learning-to-rank.ht...
In fact, the Solr conference that used to be called Lucene/Solr Revolution is now Activate and has focus on ML/AI because the topics are really starting to overlap (https://activate-conf.com/). You can see the interesting topics from last conference: https://www.youtube.com/playlist?list=PLU6n9Voqu_1FMt0C-tVNF...
Learning (Solr at least) is a different issue. There are so many features now that the Reference Guide is absolutely enormous. And the demo schemas are still a bit of a kitchen sync, making it look more complicated than it needs to be. And, the last comprehensive book was several versions back. Again, that's because Solr is big and is growing really fast still...
Actually that's why I chose to be a popularizer within the Solr community and focus on making it easier for beginners to start.
See, for example, my latest presentation slides at: https://www.slideshare.net/arafalov/rapid-solr-schema-develo... and the backing configuration repo: https://github.com/arafalov/solr-presentation-2018-may (includes smallest viable useful schema)
(tl;dr) Search is still exciting, lots of cutting edge cool stuff, and there are people trying to make it easy for beginners to start.