The Chinese AI scrapers/bots are killing quite a bit of the regular web now. YisouSpider absolutely pummeled my open source project's hosting for weeks. Like all Chinese AI scrapers, it ignores robots.txt. So forget about it respecting a Crawl-delay. If you block the user agent, it would calm down for a bit, then it would just come back again using a generic browser user agent from the same IP addresses. It does this across 10s of thousands of IPs.