It is necessary to implement the functionality: when uploading images, compress them and convert them to modern formats: avif, webp. Then display the images in the <picture> tag.
https://qna.habr.com/q/681143
https://github.com/GoogleChromeLabs/squoosh/tree/dev/libsquoosh
https://github.com/GoogleChromeLabs/squoosh/tree/dev/cli

You can also implement the functionality of creating a reduced copy of the image for the first, so as not to load the full picture. For example, in the slider there are small pictures and when you select a large one opens, but in a small picture a large one is loaded now, which negatively affects the page load.
https://developer.mozilla.org/ru/docs/Learn/HTML/Multimedia_and_embedding/Responsive_images