This is a decade+ old myth that needs to die. Both Matt Cutts (Google's search liaison before 2015) and, more recently, John Mueller (current), have said in no uncertain terms that text to HTML ratio are not ranking factors. SEO companies (and tools) will present this non-issue to clients because they are either ignorant, want an audit to look like it has a lot of issues, or they are trying to present an additional item they can bill to "fix."
"As far as I know, we don’t use the text to HTML ratio for anything. So this is something that some SEO tools came up with at some point. But from our point of view we don’t use that at all. I wouldn’t focus on a metric like that unless there is something of value you can pull out of that for the users. Maybe what you could be looking at there is seeing that these pages are bloated HTML and when you serve them to users, especially on mobile, it slows everything down. Thats one aspect that could be playing a role there, which is more between you and your users."