Inspector Lewis has always been more sizzle than steak. They certainly get an A for effort, but at best a C for execution. They have good lead characters. They try very hard to be intelligent, making "Intelligent Design" an ironic name for the last episode. They have nice music. But the stories are terrible and make very little sense.
It is possible to make such a formula work, as the early Jesse Stone episodes showed. You didn't notice how bad the stories were because Stone was such a compelling character. It doesn't work on Inspector Lewis for two reasons. First, neither Lewis nor Hathaway are quite as interesting. There is no Morse here. Given Lewis's low key, you get the feeling that show called "Inspector Hathaway" might have worked better. Second, also don't focus enough on the lives of the lead characters to make it work as a character-driven show. Instead, they fill up a lot of the time with rather boring college student angst. The secondary characters are not that interesting. The show has never been the same since without Max.
Like most people, I initially expected very little from a show about Morse's dull sidekick when it started, but was pleasantly surprised how well it worked. Then the effect of low expectations wore off. Week after week, you keep hoping for more because there is so little adult TV that you desperately want it to work. It never did. Well, it has lived off being a Morse sequel long enough.
I won't miss it but I will miss what I hoped it would be.