And Star Trek and other scifi shows gloss over the fact that just because a planet has what it needs to support Human/Vulcan/Andorian life does not mean it can. They would only have a slightly greater chance of surviving on an alien world than on their doomed one. Like I said, quick or slow death. The chances of finding a world that would not kill the Boraal is miniscule. To find one in the time allotted during Homeward would be impossible.
Humans in Trek engage in Terra Forming. From what TWoK, and TNG's Home Soil tell us is that if life is there no Terra Forming allowed.
Going from a macro to a micro scale, the Bubonic plague came Europe from Asia leaving villages barren of human life. Half the population of Europe died. Small Pox was brought from Europe to the Americas and untold millions of Native American were wiped out. Again villages were left empty. Micro invaders, in a new ecosystem killed on untold scales, and it's happened more than once in human history.