Nor is the left dead in the Netherlands - PvdA being punished for a grand coalition with its vote collapsing (most of which to non-coalition centre-left parties) is not particularly concerning.
Left-wing parties GL, SP, PvdA and PvdD have 42 out of 150 seats, fewer than ever and almost what the PvdA got on their own in 2012; back then, these four parties had 59 seats and the PvdA 38. Even if you include economically center-right D66, they went from 71 in 2012 to 61 in 2017.
I wouldn't say the left is dead in the Netherlands because I'm not some "2017 forever" person and the PvdA will get back up. However, with a party that will never form a center-left government in the driver's seat and a center-right government being all the left can hope for, the left is weaker than ever right now.
You missed Denk. Also, even liberals like D66 would've still been able to attack the PvdA from the left thanks to said coalition. As I say, grand coalitions are usually ruinous for left-of-centre parties and they get hammered for it at the next election - odd circumstances like then are not the best time to measure the health of the left in the Netherlands.