Image Optimization
One of the things I see overlooked often is image optimization. It's still important!
I've been using ImageOptim (CLI) and `cwebp` for creating WebP versions.
WebP is pretty well supported, but not fully, so I've been sticking with PNG/JPEG for WordPress sites. Can I Use
For static sites, the 11ty Image plugin is amazing. It optimizes, sizes, and outputs picture elements for supporting different sizes and fallbacks for older browsers.
Even with those tools, it's best to start with a good baseline. Size/crop the image appropriately and choose the best format for the image. I generally use PhotoShop or the Preview app on Mac.