The reason technical SEO gets skipped is that it is invisible. Nobody looking at your site can see that four hundred parameter URLs are eating your crawl budget, or that three pages are competing for the same query, or that your canonical tags point at a staging domain. The symptoms just look like "SEO is not working".
We run technical SEO as diagnosis before prescription. The first deliverable is an ordered list of what is actually wrong and what each item is likely to be worth. Plenty of technical audits return two hundred issues sorted by severity score, which is useless to a business owner deciding where to spend. Ours is sorted by impact and effort, and the top of the list is usually four or five things.