I agreed with that criticism at the time, until they actually released the game and the content was absolutely worth being it own campaign, it was in no way only 1/3rd of a game.

I mean people can complain that the story was a bit crap (and it was), but the SC story has always been crap (SC and brood war were fanfic scifi levels of bad and I still loved them).

SC2 wings of liberty is in my opinion (as a lifelong RTS fan since I played Dune II on my Amiga 1200 in 93) one of the best RTS campaigns from a pure mission gameplay standpoint, beaten only by Warcraft 3 and Red Alert 2.

As for plots in games, I honestly think all blizzards games have had crap stories with the exception of Warcraft 3.
There lore is decent, but the in game narrative has always been cheesy b-movie tier.