Hi, I am Reema, and I head Product at fastshop. I agree with Richard, using an image optimization app is your best bet. Fastshop is a media optimization app, which means we optimize both product images and product videos on your store. We have 850+ brands on Shopify stores today that we do this for, and it’s an automated app that does its job without any intervention from you. It also adds NO bloat to your website.
We have a free plan if you want to try us out!