Is it true that a wordpress site ranks better than basic html site?

Validation (95% of the time) has nothing to do with rankings. It's only if the page is so badly written that it becomes slow ... then it could have an effect on rankings.

As has already been mentioned, it has good natural linking structure and is easily updatable ... meaning it's more likely that people will post content more regularly ... leading to more IBLs .. and therefore better rankings.

And yes, it does have the auto-ping feature which enables it to be indexed quickly, but indexing is no guarantee of ranking successfully ... there are plenty of non-WP sites in the top SERPS to prove the point that it has nothing to do simply with the platform of the site... it's what that platform enables you to achieve.

In a nutshell, if you expect that moving a site from static HTML to WP will automatically increase your rankings, you'd be entirely wrong.