I finished Act 1 and am into Act 2, so a bit farther along than you, Deleyan, but my thoughts are similar! I completely agree the first bit of story where you get the combat tutorials is a little unwieldy; I think it works as a way to get you some core skills before the world opens up, but, the flashbacks are a little jarring. So far they happen very infrequently after the tutorial story section, so the beginning of the game isn't emblematic of the rest of the game.
I am thoroughly enjoying myself. I am also not super good at combat. My favorite combat systems are ones that make me work a little bit, but are also forgiving, and are satisfying to use as they're designed (aka don't feel grindy). Ghost of Tsushima fits this. It slowly adds additional mechanics (stances, ghost skills) so you can learn at a gradual pace. And standoffs NEVER get old. They are so satisfying to execute well.
I'm also finding the side quests interesting. They really are tales. Little bits of story, many of which have a twist ending of offer different perspectives on life in Tsushima. They are varied and I haven't gotten bored of them yet. The thing I love the most is the attention to detail, and how organic everything feels. From chasing golden birds to undiscovered points, to following foxes to shrines, to wandering across peasants who have quests for you, the world feels built for Jin's story. Little things, like how Jin sheathes his katana with precision and how he talks sweetly to his horse when you mount up endear me more to the character and the world.