That setup actually makes me think of 'The Beginning After the End'—except there the main character is reincarnated into a new life, not back as their own ancestor. The ancestor-with-a-system thing cranks the power fantasy to eleven, but the biggest narrative speed bump I've seen authors stumble over is emotional stakes. If you're literally the founder of the clan and you have an omnipotent system, what's left to fear? The conflict becomes weirdly administrative. Internal clan politics? You wrote the rules. External threats? You're the original badass they tell legends about. I've watched a few web novels with this premise fizzle out because the protagonist just steamrolls every obstacle by chapter thirty. The tension has to come from somewhere else, maybe a system with contradictory goals or the psychological weight of watching your descendants make the same mistakes you did centuries ago. Without that, it's just a god simulation, which gets old fast.
Some stories try to fix this by making the system itself the antagonist, giving it a hidden agenda that clashes with the ancestor's love for their family. That can work, but it often feels like a cheat, like the author realized they made their main character too powerful and had to invent a bigger bully.