Visitors don't complain about a slow site — they just leave. Speed affects both conversion and Google ranking, and most fixes are simple.
Run your site through PageSpeed Insights (free, by Google). Look at mobile scores — that's where your customers are.
Compress every image before upload, lazy-load below-the-fold media, keep one or two font families, and let a CDN cache your static files.
Bottom line: test on mobile, fix images first, put a CDN in front. Seconds saved are sales saved.