I don’t use the grammar check on Pages for Mac at home, but I do on Word for Windows and Mac at two workplaces. Even if I ignore it nine times out of ten, it saves my backside the tenth time, with all the copying/cutting, pasting, adding and deleting of text I do. A few weeks ago it flagged three instances of passive voice. It correctly identified passive voice, but its suggestions for change were wrong. (It actually flagged more than that. I took photos of three then gave up.)
Firstly, there is nothing inherently wrong with passive voice such that it needs to be flagged every time, in the same way as, say, subject-verb number disagreement, which is always wrong. Even the most anti-passive style advisers, such as Strunkandwhite and George Orwell, use passive voice perfectly when appropriate. Secondly, if you’re going to suggest changing it, then make absolutely sure that your suggestion is right.
But that is not easy for a computer to do, as these three (slightly adapted) examples show.
1) Protection is provided by defining a safety area, whose shape and dimensions must be specified according to a risk assessment.
Suggestion: Defining a safety area, whose shape, provides protection [plain wrong]
2) Alerts and reports are provided by [this software] displaying information in an intuitive and easy-to-read format.
Suggestion: [This software] displaying information in an intuitive and easy-to-read format provides alerts and reports [mostly wrong]
3) Areas of the multi-purpose centre have already been made available for use by community groups offering support and services to [this organisation’s] customers.
Suggestion: Community groups offering support and services to [this organisation’s] customers have already made areas of the multi-purpose centre available for use [possibly right, but not]