I understand that you’re getting that message. Just because someone suggests that you do something doesn’t mean that it’s a good idea.
What text do you propose be put into H2 to H6 tags?
Note that H4 to H6 tags are fairly rarely used, so unless you contrive to stick stuff in them, you’re still going to get a warning for those. You’ll be hard pressed to find any pages on the internet that use all 6 H tags.