What was revealed by science that disappointed you the most about reality?

Nothing about science disappoints me. It is just a process that is about seeking the truth. The truth and reality are better than any other alternatives.

If you want to explore the universe you have more probelms than just not being able to travel at the speed of light. First, there is the lack of technology for doing it with. You also have the problem of not enough time. The universe has a diameter of 93 thousand million light years. Therefore, travelling at the speed of light you would need 93 thousand years to cross it. You simply do not have that long.

That there is no realistic way to explore space "Star Trek" style due to the combination of huge distances and time dilation.

This couples with the SciFi idea that there are other things to be discovered in physics that will allow us to do anti gravity / teleport / tractor beam etc. Because basically there aren't any practically usable things (forces / particles) left to be discovered or we would have seen them at Cern. All our advances in technology will be material science, processing power and clever engineering but no one is going to find something new like gravity or magnetism because there isn't any gap for it fit in in the standard model. Any new stuff is going to be at extremes like in black holes or only operate at the scale of galaxies.