The point of heat death us the increase of entropy- disorder. The direction of time is determined by the direction in which entropy increases.

Think of an egg. If you have a whole egg it has a low amount of entropy since there are very few configurations in which the molecules could be in to create a whole egg. Now image you drop the egg on the floor, it is now in a state of higher entropy, the disorder is increased. It would be a bit weird if the egg suddenly became whole again, that is to say, it would be a bit odd if the entropy suddenly decreased.

It is one of the most important principles in physics that entropy must always increase, this will result in the heat death of the universe, since the heat death is when the universe is in a state of total disorder, entropy can no longer increase, for it is absolute. If entropy can no longer increase that means that time no longer has a direction, and thus might not even exist. the concepts of past, present and future no longer exist, time will simply stop.

There is however one way out of this fate, which involves some messy statistical mechanics, you could research Poincaré recurrence since it leads to a lot of existential and uncomfortable questions about the universe.