Here’s one little report which is worth checking. You’ll find it in Google Search Console (which you do have running, I hope). Just click on ‘Search Appearance’ and ‘HTML Improvements’, and you’ll get a nice list of ways in which you can improve your on-page SEO. Here’s what it looks like:
When playing with other tools that give you this sort of information, most of us probably think: “Does Google care about all this?” Here’s your answer. It cares enough about these particular issues to create and maintain its own report saying that they can and should be improved.
If you’ve got ‘duplicate title tags’ (or meta descriptions), it could be an indication that the same page is appearing multiple times to Google under different guises, and this probably needs to be solved using a canonical URL.
More likely, you actually have different pages with the same title tags or meta descriptions. See this as a big opportunity. Write more relevant tags, and give the pages far more of a chance of ranking for their key search terms.