Part of it probably has to do with the fact that people who grew up with SC are older now, and it's easier to see flaws in the story.
That's exactly it, their views of SC1 are wrapped in nostalgia-laden cotton wool- the story of SC1/BW is every bit as silly and full of terrible dialogue. That article is a prime example, the author obviously holds SC1 in a shining light and ignores how the original games used the Xel'Naga to fill in numerous holes in the plot, while providing next-no-information on the Xel'Naga themselves, how stupid the "oh Kerrigan seems ok now, let's work with her" plot device in Brood War was, how you play the über-talented new commander/cerebrate who can do no wrong (and he's whinging about this being the case for Raynor in SC2!) and so on. The vast majority of that article is just personal opinion, e.g. "Kerrigan shouldnt have had obvious vulnerabilities like the Space Station which was the hub for the majority of zerg fliers, or the nydus tunnels which could be easily flooded with lava.", combine that with the author's love for Mass Effect, which is far worse than SC2 when it comes to the majority of the complaints the author made, and you have something that's quite hard to take seriously.
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I'm also debating. A lot of the reviews didn't think highly of it. Lack of a good campaign and not a lot added to the multiplayer were the main complaints. I'd love to hear from anyone who has it!
The campaign is fantastic. The multiplayer is in need of a balance update at the moment, but is still great. Widow Mines are stupidly powerful for how little they cost and how quick they are to get out onto the field- they need to be nerfed, otherwise the things that define Zerg play, speed, map control and numbers, are ruined. I.e. one mine shouldn't be able to one-shot 20 Zerglings.