Excerpt from the article
"Unfortunately despite my fondness of the Killzone series, Killzone never became what Sony needed it to. The original Killzone whilst a relatively solid game was very rough around the edges, although at the time I was blown away by its technical prowess. I’d never played a game before where the gunplay felt quite so meaty and visceral. Unfortunately this wasn’t the consensual opinion of reviewers at the time, the lack of polish exerted by the game lent it to a relatively modest critical reception."
The author goes on to describe why he thinks Guerilla games latest title would have been better as a new IP.