I used Solr back in 2008-2009 or so and it did a great job, but people didn't like that it used XML rather than JSON. Then we had a requirement for something like Elasticsearch's percolate query functionality, which Solr didn't support. So we switched, and subsequent projects I've joined have all used ES.

As I understand, Solr now has a JSON REST API and it's improved in other ways over the years, but ES has quite a bit more mindshare these days: https://books.google.com/ngrams/graph?content=solr%2Celastic...

So now in addition to the "does it do the job?" question, teams might also ask "can we hire and retain people to work with this technology rather than the more popular alternative?".