As a frequent user of Cressington I am naturally miffed when our station has to put up with a poorer service. But I appreciate that compared to most local stations nationwide we get a good deal.
The Hunts Cross branch as a whole, though, deserves an all-day frequent service. Leaving aside South Parkway, St Michael's is very well used, and the all-hours popularity of Lark Lane, let alone events in Sefton Park, means that it really deserves a metro frequency throughout the day. Baltic, when/if it finally materialises, even more so: no-one is going to hang around for half an hour when they can get a bus within a couple of minutes or walk into/from town in twenty minutes.
Unlike north of Moorfields on the Northern Line, or the Birkenhead end of the Wirral, those stations are not served by multiple services and hence get a less frequent service than most other stations the same distance from the city centre. So either there needs to be turn-back provision at St Michaels, or the frequency through to Parkway (at least) should be doubled.