The opponent in a single-player game is the AI and the conditions given by the game much like trying to get a high-score in a 1P game of Asteroids or Star Castle. In current Starsector, it is beat never-ending fleets of AI efficiently enough that the player does not death-spiral into a perpetual state of poverty and endless respawning (the closest Starsector gets to a true "GAME OVER"). I do not cheat (on my first playthrough) because there is no point - just say "I WIN!" and move on. Loophole abuse and AI/game exploits is not cheating, because I did not break any rules enforced by the game.
As for Ironman, since player can leave the game without saving by exiting combat, player can save-scum there too. It just takes longer because the game exits to desktop instead of going to the main menu. Since the game provides non-Ironman, I use it, because I do not want to waste a minute or so exiting and restarting the game. If current Ironman was the only way to play the game, you bet I will save-scum there (and get irritated by constant exit-and-restart). For Ironman in Starsector to be like Ironman in Roguelikes, save-scumming should be impossible unless the player backs up files manually; then, it is cheating to save-scum.
Also, the game intends fleet action play, but soloing fleets with one overpowered ship is much more efficient in CR and supply consumption, and protects your AI ships from themselves, which is why I solo nearly every fight in the game. This is not cheating. What the developer (or lawmaker) intends and what the game rules (or law) actually says and enforces may be two very different things, which is why there are amendments, errata, patches, or the like to mitigate or remove exploits or degenerate play. Telling me that I cheat just because it offends people idea of a fun game instead of actually breaking game rules is just trash talk by an opposing party trying to shame a gullible opponent to give up and join them. It helps that Starsector is an "alpha", so that exploits found have a chance to be addressed.