Speed is the platform's real gap
Squarespace serves responsive image derivatives, but only from the source files provided, so a 6MB hero upload becomes a slow page on every device. Add full-bleed video, fifty-image galleries loading at once, several webfonts and a few third-party scripts, and field-data Core Web Vitals go red on precisely the visual pages that sell the business. Subtractive work fixes most of it: size and compress before upload, paginate galleries, kill autoplay video above the fold, audit injected scripts.