How important is it to include subjunctive phrases where possible in Spanish prose and why?

In Spanish, the subjunctive tense is used to express doubt, uncertainty, wishes, demands and is often used after prepositional phrases expressing opinion or mood. In essay writing, it is generally important to use the subjunctive tense to a certain extent to show that you are able to seamlessly switch between tenses, and to demonstrate one's breadth of linguistic knowledge. Subjunctive phrases can be especially useful in conveying ideas shrouded in doubt, although it is imperative to integrate subjunctive phrases into an argument, as overuse of these phrases can lead to the detraction of their meaning and purpose within a sentence. One should also be careful to not use the subjunctive where it is unnecessary, a mistake often made by Spanish students, i.e. in sentences that do not express doubt or uncertainty such as 'creo que...' as opposed to 'no creo que...' (where subjunctive is necessary).