A good technical SEO expert needs to rely on various skills and personal traits to perform well. The main skill recruiters demand in a dedicated technical SEO role, beside general understanding of SEO best practice, is a solid understanding of coding. This is mainly front-end code (HTML, CSS, JS) with a focus on functionality and accessibility, but server-side languages are also impressive when applying for technical SEO positions. Familiarity with various CMS and site management systems (such as WordPress, Magento, Drupal, Joomla, Shopify, etc), from a user perspective and from a developer perspective, is also extremely useful for agencies.
An intimate instinct for Google’s ethical principles, policies & preferences is also vital to being a successful senior technical SEO specialist who doesn’t waste time & resources working on trivial, irrelevant things that often even do more harm than good in some cases.