It got slower while I optimized it
I added lazy loading to every image on a site in about 20 minutes, felt pleased with myself, and then measured it and found the pages were taking longer to show their main content than before I started.
What the CMS does to your hero image
I got a homepage's hero down to 180 KB in January, it's 2.4 MB now, and the only thing anybody did was change the picture through the form that exists for changing the picture.
The 400 KB hero
Every conversation about page weight goes straight to minification. Meanwhile there is a 2 MB image on the page that nobody has opened since Photoshop.