There are no shortage of anime which put a mecha genre spin on the “modern-day character ends up in fantasy/alien world” (isekai) theme. From Aura Battler Dunbine through arguably series like Orguss into ones like Magic Knight Rayearth or The Visions of Escaflowne it has strong precedent, and it is a genre that brings a few additional interesting themes to the traditional science-fiction and fantasy ones. I am personally very interested in stories of culture shock, or outsiders to a society trying to fit in; it is for this reason I was quite disappointed in the TV adaptation of Crest of the Stars because it hinted at being a story of a human living as the ward of aliens and learning their culture, and then did not really deliver so much on that. One could almost consider, actually, a story like Crest of the Stars as the pure science-fiction equivalent to the isekai story – a human living among aliens.
A lot of fantasy and SF fiction, especially within anime, focuses on the hero as the central viewpoint character, or if the protagonist is not particularly heroic it will tell the story of their development as a hero or desire to become one. Generally this is through gaining physical strength, or fulfilling some quest. Even fish-out-of-water stories, in which a new protagonist tend towards this predictable plot arc, with other narratives stopping or becoming rapidly repurposed to assist the new viewpoint character. In essence, it is generally the case in genre fiction that the viewpoint character will be given significant agency in the main narrative; the epitome of this is The Lord of the Rings, which focuses strongly on how it is the inherently unassuming nature of its protagonists which is their greatest strength. The hobbits are out of their depths, but nevertheless are integral to the quest and ultimately are revealed to have an innate heroism which is superior to the strength of arms of their companions.