Where did all the heavy/assault weapons come from? They're not that prevalent in the UK 
The story just seemed to be badly thought out idea after badly thought out idea. Lots of inconsistencies (e.g. if you can avoid being blind by not looking at the sun, the half of the world that was asleep at the time would be fine). Far too much deus ex machina, which was used practically every 5 minutes to get out of situations. Whilst you can forgive occasional use, using it to get out of every scene becomes incredibly tiresome.
The central idea that carnivorous triffids produce a crude oil substitute was also annoying... that they require meat to produce the oil was just laughable. Where are they getting the meat from? From cows grazing on grass? So the energy is going sun > grass > cow > triffid > oil > your car. Modern biofuels (e.g. ethanol fuel produced from sugar cane) are already more efficient than that convoluted process.
I like my sci fi to be reasonably intelligent, but this didn't have the production value of The Day After Tomorrow to get away with a shockingly bad concept.
All in all, I think the reason people are moaning is that it could be a good idea. It had promise, but it was a spectacularly failed opportunity.

The story just seemed to be badly thought out idea after badly thought out idea. Lots of inconsistencies (e.g. if you can avoid being blind by not looking at the sun, the half of the world that was asleep at the time would be fine). Far too much deus ex machina, which was used practically every 5 minutes to get out of situations. Whilst you can forgive occasional use, using it to get out of every scene becomes incredibly tiresome.
The central idea that carnivorous triffids produce a crude oil substitute was also annoying... that they require meat to produce the oil was just laughable. Where are they getting the meat from? From cows grazing on grass? So the energy is going sun > grass > cow > triffid > oil > your car. Modern biofuels (e.g. ethanol fuel produced from sugar cane) are already more efficient than that convoluted process.
I like my sci fi to be reasonably intelligent, but this didn't have the production value of The Day After Tomorrow to get away with a shockingly bad concept.
All in all, I think the reason people are moaning is that it could be a good idea. It had promise, but it was a spectacularly failed opportunity.