SO WHY DIDNT THIS WORK THIS TIME ?

Nowhere near as good as the original's 1st season but still decent. I personally hope there'll be another season, possibly on Netflix or similar. Enjoyed it.

I have some opinions on why it didn't work.

Characters were under-developed and we couldn't care less about:
The Twins: No back story. What backstory they had was flimsy and weak. The girl's powers were so horribly defined. Her personality was wish-washy and weak. She was so hard to care about. The boy's powers drained powers around him? Why didn't it drain everyone's? Why just Hiro's? And them needing a conduit to use their powers together was lame.
Joanna was unlikable from the beginning. Despite her story, she was still an awful person. Even when she found out it wasn't evo's that caused her son's death she was still 100% eager to kill them. When she found out it was Erika's fault, she worked WITH Erika. Seriously? That was flawed.
Speaking of Erika, she was supposed to be a bad-ass evil chick. She had no backstory, no reason why she was this way. Just that she was. At least with Sylar, we had history. There was nothing about her that seemed to validate why she wanted to kill all evos while using them.

Characters from the past that we loved:
Matt Parkman: They made him an evil bastard. That's seriously screwed up. I hated every moment he was on screen because he was an amazingly good guy.
Hiro: He was in the show about five minutes, his powers were drained (and only his) by the kid. Hiro was one of our favorites, we wanted him to be present.
HRG: His story line was just...meh. And him having to be the conduit for the twins? That was lame
Nathan and Peter Petrelli: How I missed them. Peter was one of the best parts of Heroes, and he was completely missing. Not even mentioned?

The end that they had to battle against was somewhat clear in Heroes, but this 'end of the world' thing was confusing up until the very end.

The whole show wasn't as well done as the original. It was a terrible let down.

not sure. it was one of my favorite shows.

Starting out with inflationary use of powers. Half into the season they are already deep into time travel and all that crap, which inevitably lets a story fall apart.

There are two ideas which can make superpowers fun:
1. discovering the power and learning to use it
2. reaching the limit of the power and that way integrating it back into a concept of human interaction and conventional wit.

Everything else is mere eyecandy and when used too often, will make the result as boring as this show.
Both ideas require to define the rules of the power and let the person wielding it act accordingly. This show however just sprinkles the powers as some deus ex machina over the plot: A power will do everything to create the certain situation the screenwriters need.