Google search advocate John Mueller has always downplayed the value of HTML sitemaps. Recently, he reiterated his dissatisfaction with HTML sitemaps, saying:
“I changed my mind on HTML sitemaps over the years, they should never be needed. Sites small [and] large should always have a clear navigational structure.”
This is a slightly stronger stance than what he’s expressed in the past:
“When it comes to SEO … for small sites, your site should be crawlable anyway (and if you’re using a common CMS, it’ll almost always be fine) & for large sites, they’re not going to be useful anyway (use sitemaps, use normal cross-linking, check with a crawler of your choice).”
