The honest version: WordPress isn't the problem, the way most agencies build on it is. A stack of a dozen plugins and a page builder theme will always be heavier than a hand-coded build, and that weight shows up in your Core Web Vitals and, eventually, your rankings. We've written up the trade-offs in detail in our piece on page builder themes like Divi.
Whichever route you take, the ongoing care is the same: we handle updates, backups, security and edits as part of our managed plan, and the local SEO groundwork is included either way. If you're weighing up a shop, start with whether you actually need an ecommerce website before committing to WooCommerce.