I do not understand the negative feedback. Luckily I discovered these poor review after I watched a few episodes, or else I would have missed out on a great TV show.
I was sad when it ended, as I wanted to know more, how they survive with these ice age conditions and animals, where are the other 'modern' people who fell into the sinkhole at different earlier dates, what they did with their technologies. I will admit I expect to see more technology used and more people made it through the sinkhole given that multiple sky high buildings fell through.
Regardless, the plot line is solid. Keep it up and roll on Season 2.