In his Oct 2, 2019 blog article, SEO Round Table’s Gary Schwartz has reported that Google’s John Mueller posted on Reddit that he agrees, that HTML sitemaps are not worthwhile for SEO purposes.
See Gary’s article here: https://www.seroundtable.com/google-html-sitemaps-seo-28312.html
I’ve been in SEO for as long as SEO has existed and I’ll agree with John Mueller on this issue.
In my opinion, web site developers should be more focused on simplification of their site’s navigation. If it is simple, it is good for people and for search engine bots.
I’ve spent time and money in the past creating very large site maps using tools like Screaming Frog software to index and create sitemaps of my site. Screaming Frog’s prices eventually increased too much over a couple of years so I stopped using them and briefly considered writing my own tools to do the same thing.
In the end, I used my time to focus on design improvement including a major simplification in the U/I which dramatically reduced the amount of links per page making it easier for people to navigate as well as Google, Bing and Yahoo search engine bots.
Don’t waste your time with sitemaps, use your time more wisely on design improvements.