I agree. The devs couldn't continue working on CS 1 forever, and eventually a sequel would HAVE to be made somehow. It was never going to please everybody, no matter what they did. Im glad that, despite the controversy, CS: Source still ended up being good.
I remember I got it for GMod, and played it out of boredom one day and I ended up loving it!
You have to remember, these kinds of games ingrain heavy habits. You get a feel for various nuances in the game (eg shooting people through a wall, recoil of a certain people). They may feel surface level but it can be jarring when it all gets changed.