Is raw SQL bad?

Question

Python

Preface.
I'm learning Flask with this tutorial . There is a chapter where text search functionality is added using Elasticsearch. In this case, a problem arises, which the author describes, the desynchronization of the database and the engine.
Actually a question.
Is using SQL to implement this functionality bad? If yes, why? What difficulties may be encountered in the future, with the support of such a site?