Not mine, if you thought I could do such a thing, but a finely articulate argument and analysis from Phil over at Actually Existing. Phil admits that Torchwood is tosh (and by Medium Rob's scarcely spoilering review, episode three travels further down this line) but Phil provides a wonderful discussion of the core features of RTD's work that make it both appealing and dictate its focus. I'll let you read it for yourself, but it is one of the clearest pieces I've read on why some find RTD's work difficult to appreciate.
For me, I guess that I have a certain sympathy with the three core concerns, albeit that I can equally be enthralled by darkness, wickedness and internal character believability. Sometimes that's IS what I want, but lightness too has its place and it is nice to see it so well explained by Phil in his post.