Why such a low rating?

no,

Yes, you should start watching it and then make your own conclusions.
I wanted to like this show when it was current and saw many episodes, since I enjoyed the original CSI and like a lot of police procedurals. But I don't find Caruso all that interesting to watch (at least here), the cast members seem to have no chemistry with one another, and I recall some heavy-handed stylistic touches that seemed to cover for some uninspired direction and story telling.
But that said, it's got enough razzle-dazzle with great looking guest stars and locales that I suppose one can find it exhilarating, so you really should give it a try. Ultimately I really don't and even dis-like it, but it has top notch production values. For a while I was taken with Emily Proctor and her detached, observant yet not entirely cool demeanor and interesting accent, and one of the male co-stars ("Eric" on the show?) seemed okay, but the more I watched it, the more I saw what I found to be flaws.
Maybe the crimes and trying to figure them out is fun, I'll give it that, but Caruso in particular I find unappealing, along with the very stylized production and editing.