Is H1, H2, H3 important for SEO?

[Jane]

In the larger scheme of things, they have limited weightage. But it is just one of many things to do right to succeed. All these together convey what the page is about when Google tries to match a search query with a website.

So a well structured page will convey this more clearly than a not so well structured page. In that sense, using H1, H2, H3 correctly is important. But that in itself will have some influence in your rankings depending on how competitive the search query is.