I personally love the realism and slow pace.....its a refreshing change from the quick gratification and crazy action of most of today's AAA games, but do think the controls are frustrating and can see how some might find it boring.
Same, I'm enjoying taking my time with it, it's a pleasure jjust riding through the environments taking it all in, doing a bit of exploring along the way. It somehow manages to feel less like you're being distracted from the main storyline and instead just encountering these things in a very organic way. The attention to detail is utterly absurd, and the game has surely (hopefully) set the bar very high for other developers to match in terms of NPCs, dialogue, and character animations. I love how things you pick up in the world are actually picked up and put in the satchel, and plants are pulled out of the ground and stripped. It makes the most recent Tomb Raider look like even less polished than it did already.
I do think Rockstar could have perhaps done more to communicate with fans what sort of game they were going for here, and the pace at which it plays out. That said, despite all these extra mechanics around hunting, eating, looking after the camp and the horse etc, they don't really come across as being too intrusive, certainly not to the way I'm playing anyway.
Combat is about the only thing I do find frustrating, largely because of the controls which can feel quite clunky in the heat of the moment.