If the application is rather big (relatively, more than 2-3 vyuha and 1-2 models) and could get complicated in the future, I think it is necessary to do at least 1 blueprint (e.g., core or common). Then, the complexity of the applications don't have to break bluprint the whole application, and it will be possible to make something from the first blueprint in individual. If the application is a little more complicated and will not be-the sense and in the same blueprint no.
In fact, bluprint in Flask-it is about dealing with complexity, because to reuse code in different projects in the Flask offered to do the extensions. Therefore, we need blueprint or not, and if needed, how much -- depends on how they simplify understanding of the application source code and navigate to the source code of the application.