Are metadescriptions really necessary for good seo?

[holacarinados]

I see a million ads for increasing one's SEO that include basics like meta tags, metadescriptions, etc. I checked my blog on hubspot. It has a 99% rating out of 100% and is approximately ranked 2,200 out of 315,000 blogs. Now, I have NO metadescriptions in the blog--at least the hubspot spider couldn't find any, and that was in its report. So are these rules of thumb about SEO pretty unreliable or are there so many things that go into seo optimization, the lack of something doesn't necessarily matter. All I do on my blog is blog without any gimmicks