1. I think the past, particularly the pastoral times, can be seen as utopian because it is a return to form. This is how it was. There was no late-stage industrial capitalism. No select few incessantly hoarding wealth and power. No starvation or world hunger. In this regard, it may be seen as better. Utopian, even. And as enticing as this ideation is, it is still important to remember what modernity has allowed humans to do. The distribution of art, whether than be literature or architecture or sculpture and so on. The contribution of medical and scientific achievements. The capacity for widespread communication through technology.
With all this said, I think the pastoral times tend to be idealized as a utopian society because of the economics involved. All of the things I mentioned that seem absent in both depictions of pastoral times and depictions of utopias have to do with the current economic state. But the hole-in-the-ground toilets are generally not included either. It seems to me the traditional idea of utopia follows the economic pattern of pastoral times (i.e. communal distribution and sharing) with the technology of today (or of tomorrow).
2. Of the two options, personally I prefer the science fiction genre. And I think this may have something to do with my previous answer. As I said, fantasy is a return to form. To me, it is a reflection of how the author saw the past. Science fiction, meanwhile, seems to me to be a reflection of how the author sees the future (or how they see the possibility for the future, whether good or bad: what we as a society may be hurtling ourselves into). Robinson's allusions to the consequences of climate change are a good example of this. Le Guin’s allusions to the consequences of scientism also comes to mind. These are accessible, tangible ideas to me. I can pick them up, hold them, see them. The early stages of the consequences are in the world today. Fantasy often feels hard to reach, which makes it hard to connect to. Perhaps this is due to the critique of their relationships to their utopian and dystopian impulses.