XML question

[Linked]

I have a 20 years old html site map I made. It not SML, but It works good. Google goes from homepage to the sitemap and then all inner pages. Is an XML vital for SEO? You see it come up in audits if you don't have it. An XML company said not to worry about it. But good to post. Thanks.

[RH-Calvin]

XML sitemap is a coded sitemap used to submit in webmaster tool to help spiders crawl them and index the webpages in search engines.