I didn't watch Days with My Stepsister, but if you believe AC, then it was the best thing since sliced bread apparently. The fanbase must at least be pretty dedicated to bring out the vote to such an extent.
Everything I have seen about it indicates that it is actually a serious drama about finding yourself in a step-sibling relationship with somebody that you develop feelings for. The title makes it sound suspicious as hell, but none of the tags on AniList or discussion I have seen here from those that have watched it make it seem like incest bait.
Relationships between step-siblings can and do actually happen in real life. I actually know of one example in my extended family of step-siblings marrying (though I was born in Alabama, so take that with a grain of salt). So, having a fictional story that is a serious take on the taboo nature of that relationship isn't necessarily a terrible thing, but the title definitely warrants a double take.
I only watched the first 3 episodes, but it handled things pretty well up to that point. The characters were mature which was quite appealing. I only dropped it because I have limited time and need to choose what I watch.