Arrow’s impossibility theorem just states that strictly speaking, there is no system within a particular subset of voting systems that is guaranteed to be immune from spoilers affecting the outcome. So not only are you using an overly strict definition of democracy that doesn’t even encompass all democratic systems implemented today, let alone all the ones that could be (which again, includes anarchism), but you’re disqualifying things based on not meeting a level of perfection that is unreasonable to expect of anything. It’s not like anarchism would be free of irrelevant factors affecting decisions; it would be a lot more affected by relationships between people and people’s standing in a community for one thing.

None of the problems you point out are innate to democracy. The reason you associate them with democracy is not because of any inherent quality of democracy, but because of history. To simplify things a lot, the people who championed democracy back in the days of absolute monarchies and nobility also championed a liberal economy. At the time that would have made sense, since it was seen as more fair and meritocratic than an economy managed by the nobility. And compared to that it was, but ultimate it just ended up creating a new nobility in all but name.

But just because they were wrong about one thing doesn’t mean they were wrong about everything. You can pick and choose ideas, and the anarchism you’re promoting is one such attempt.