Humans have evovled over millions of years to live in the Earth bubble. We have got to the moon so far. In a portable Earth bubble. Yet even this trip has issues around gravity. Stay in your space ship too long and your body evolves into lack of muscle.
For Humans to live on other planets these have to be identical to Earth. If not then we need to evolve into something new to survive on the new planet. Unless we take an Earth bubble with us like a habitat.
Apart from gettng new resources and removing the risk of being wiped out. There is little to be gained apart from the journey and potential knowledge.
We could meet other life forms, of which there will be many. The reality is we would be seen as an invasive species. We currently do not have the ability to travel far and may never get past our solor system. It may take many life times to travel to somewhere else. If we look at our motivation then we may find alien motivation or inability not to look for others. We are quite hostile to others on Earth, aliens would be treated worse if we where the explorers.
If we do leave the Earth bubble we would have to evelove into something that would stop being human. Failing to evolve into a new species within potential new Earths would mean inevitble extinction.
This planet has changed over may million years and will continue. So will the Earth bubble and so must we. Any new world will also have its own climate that will force evolutinary changes. These could be completely divergent to Earth. Leading to a no return option for the Human like civilisation.
I look forward to your response