I don't think there is any way you can pull a list of "less active" members. That information is not tracked in MLS or LCR. As stated above, it is easy to create a custom report in MLS that lists the members where their spouse is "not a member." Bear in mind, though, that many less active singles are actually married but the marriage is not recorded so they will not show up on this list (and conversely, some less active married members may no longer be married).
You can export and import custom report "structures" in MLS and I have one that works well for our ward. If you want a copy, PM me and I'll send you the report in a format that you can import into MLS (and it will be ready to run with your data). This export is only the report rules - it contains no data and has no private information. Using this feature, a stake can take a report they like and pass it to all their units for duplication.
I built a work instruction on how to export/import the file to MLS I will send with it for anyone who wants to try this and doesn't know how. With most of the membership functions moving to LCR, many do not use MLS much (my assistant clerk - membership is completely lost in MLS, though he is good in LCR).