You’re missing what that means for the users. It‘ not like they see a blank screen until the 2 MB are fully loaded. The page rendering will start exactly at the same time, with or without lazyload, if the image dimensions are known. With lazyload, there might be a tiny loading advantage above-the-fold and then a disadvantage of newly introduced wait time while scrolling. Without lazyload you don’t have that scrolling wait time, but a slightly slower above-the-fold finish time. Again, I tested this and could not see clear benefits for a typical use of my template products and even a considerably worse experience in some cases.
You could, but I do not recommend it. If you modify any template, you can’t receive updates for it anymore.
Also keep in mind that native browser lazyload is coming. I’m happy to support that in the future, since it is a proper and elegant solution. JavaScript-based lazyload really is not.