Elasticsearch is a search engine. It is optimised to return the best fitting results to a query at the first page. But if you want to retrieve all results for a query (which is a common usecase for DBs) the performance of elasticsearch will plummet.
For example:
Try to retrieve a list of all the 10000 movies you stored in an Elasticsearch index. You will get the first 100 results easily, but is you scroll through the results, you will notice that elasticsearch will become very slow.
It is not optimized for that use case. Otherwise it would be called ElasticDB.
