It's amazing the amount of rubbish that gets written about URL's and "SEO".
In truth, the URL itself is negligible in terms of "SEO". It can be LONG, in can be SHORT, it can be DYNAMIC, it can be STATIC...
The important thing is NOT the URL, but what lies BEHIND it !!! What does it reveal to the search engine, once it is "opened"?
It is nothing more than a front door. It is the GATEWAY to specific PAGE CONTENT, and complementary site NAVIGATION.
What search engines want, is that when a URL is accessed, does that URL deliver good, logical content and on-linking, and meaningful, clear FUNCTIONALITY?
Does the URL generate (or reveal) a page that provides a good, valuable user experience, that is easy to follow, is of importance to the visitor, and that loads quickly and has all its resources properly compiled and displayed.
The URL itself has absolutely NO INFLUENCE on the Search Engines' subsequent indexing and ranking of the page.
A BADLY COMPOSED URL - (such as a "dynamic" url that does not offer up (generate) complete content, or from which FUNCTIONS may seem confusing or irrelevant, or through which other links do not seem to follow a logical pattern) - will need attention, NOT because it is "badly named" but because it is delivering BAD CONTENT.