The Morlocks are sort of a writing master class in how to create unlovable antagonists. They live underground, they eat people, they're compared to various unpopular animals (like rats and spiders), and they never get to tell their side of the story. They're creepy and monstrous, and they keep trying to eat our main character. Oh, and they steal his Time Machine and then use it as bait to trap him. If they had moustaches, the Morlocks would be twirling them. Even though the Time Traveller doesn't feel any pity for them, we have to recognize that the Morlocks are our descendents, just as much as the Eloi are. That may be the worst thing of all about them.
Well, it might not be right to call "Time" an antagonist exactly, but Time is definitely one of the major issues/obstacles the Time Traveller faces. We don't mean that it's Time that prevents him from getting home – that's the Morlocks. What Time does is allow the world to change radically and become a place that's incomprehensible to the Time Traveller. You could look at it another way, though, and say that Time – great, huge amounts of Time – is what opens his eyes to what's really important in the world (hint: not him). So Time may be less an antagonist and more like a mentor teaching him an incredibly important but unpleasant lesson.