Systematic review is the first step in answering any research/policy/practice question. The only way to find the answer is to find and check all the relevant answers and literature systematically, neither randomly, nor selectively! There are 48 types of literature review with some ‘systematic’ components. The type of the review you choose depends on your needs, time, and resources.
Systematic review is the only way to assure you that you are not missing anything and your work has novelty and is not a duplicate. Either it is your personal work or a grant application, it starts with a systematic review, continues with systematic review and ends with it.
See the last lecture on Computer Programs for Semi-Automation of Evidence Synthesis