Episodes are so formulaic, it's almost funny. There's a murder. DI Poole investigates and narrows it down to a handful of potential killers. There's usually another murder. Then Poole has a lightbulb moment, gathers all the suspects in one room and gives a Poirot-esque speech explaining everything. This is undemanding drama for the hard-of-thinking or only-half-watching. See also the copious recaps and clunky exposition that litter the script, just in case anyone nodded off and missed a bit. Which would be understandable. It makes Midsomer Murders look like 24.
You've got to admit - he's got a point...
Hang on, the same could be said for just about anything, Doctor Who, CSI, Mentalist, Castle, etc, etc, we all know what's going to happen and how it will end, what matters is the bits in between.
Which, in my opinion are very good bits indeed!!