I'm not sure the efficiency of the whole of humanity on earth and the efficiency of a comparably tiny colonial group is related in any way. There's a ton of momentum to overcome here on earth, and any change will need to occur across vast swaths of the population to be effective. That's an extremely tall order and it's extremely unlikely, as humans tend to ignore impending danger if there's no immediate consequence involved. Significant change will be seen at a generational pace at best.

Colonists, on the other hand, must be efficient if they wish to exist for longer than a few weeks, and they're a small and smart enough of a group that maintaining efficiency isn't an issue. Efficiency is a way of life for them. If anything, extremely low waste yet modern lifestyles will get their start in planetary colonies and make their way back to earth, not vice versa.

Perhaps there are advantages that other planets have, that we don't have on earth.

There are certainly massive disadvantages, life support, ect, but there could be things like large amounts of plentiful fuel.

Well, if the Earth really gets that bad (e.g. the entire surface is all water, no land; or extremely destructive weather events; or too dark because sunlight can't reach our surface), it might actually be easier to set up self-contained (bubble) cities on another planet than on earth itself.

But if you're talking about terraforming, then if we could terraform another planet we could probably re-terraform earth itself.