Which phrase best captures the essence of 'fortuitous'?

The phrase that best captures the essence of 'fortuitous' is one that emphasizes an unexpected occurrence that yields a positive outcome. 'Fortuitous' refers to events that happen by chance in a way that is fortunate or beneficial. Therefore, unplanned yet favorable circumstances align with the definition of the word.

While the other phrases describe different situations, they don't reflect the serendipitous nature of 'fortuitous.' For instance, 'deliberate and systematic' conveys a sense of intention and planned action, which contrasts sharply with the randomness implied by 'fortuitous.' Similarly, 'complicated and confusing' suggests a lack of clarity or direct benefits, and 'neglected and overlooked' signifies something that has been ignored and does not carry the implication of a fortunate chance encounter. Hence, the selection of 'unplanned but beneficial' aligns perfectly with the meaning of 'fortuitous.'