In a video on YouTube, Google’s John Mueller said that a higher crawl rate does not mean that a website gets higher rankings on Google. You can get high rankings even if your website does not have a high crawl frequency.
Now John Mueller confirmed on Twitter that it does not have to be a bad thing if your website has a low crawl rate:
That's not necessarily a bad thing; some sites just don't change a lot, some are just less interesting, every site's different.— John ☆.o(≧▽≦)o.☆ (@JohnMu) 5. Juni 2017
John Muellers previous statements on that topic can be found here:
Make sure that Google can crawl all of your pages
If your web pages contain errors, chances are that Google cannot index all of your pages correctly. The website audit tool in SEOprofiler helps you to make sure that Google can index all of your pages: