You can comparably do a lot by making your own engine, if you know what you're doing. Stardew Valley was written in XNA but other than that there's no engine. Lots of games written in monogame, SDL, SFML, PyGame, and other "frameworks". People also think that a 3D engine is absurdly hard but that's because they spend most of their time implementing PBR and a full featured level editor in their own custom UI framework. If you use off the shelf parts for things like physics, UI, and implement common file formats for levels then you can focus on the things you find interesting and still make a game. I'd wager there's a lot more unfished unity projects than unfinished game engine projects
