Usually, No
Commercial WordPress themes generally include a large suite of scripts and styles, along with a comprehensive set of features in order to make them pop.
Most premium themes rely on a number of theme options, various widgets, eventually some sliders, content builders, galleries, social media integrations and the like.
Each of those components is written in PHP and often includes some JavaScript and CSS assets loaded separately. Those increase the load times due to the larger number of parallel HTTP requests for rendering a single page. Fonts and images may also get in the way.
Light, Simple Commercial Themes May Work Faster
Most of the commercial themes – especially the multipurpose ones – are simply trying to solve a large set of problems for different industries and types of websites. That’s what causes delays, instability, and possible security issues.
As a rule of thumb, the free themes hosted on WordPress.org only care about the presentation layer – usually comprised of markup and CSS. They’re fairly lightweight and simple, going through a rough reviewing process. The general principle of themes is that they should only serve for presentation of the standard blog/CMS content. Anything else should be distributed as a separate plugin – in order to keep things separated and avoid a theme lockdown whenever you decide to redesign your website.
