I'm not sure what Netlify is doing, but the heaviest assets on your website are your javascript sources. Have you considered hosting those on GitHub pages, which has a generous free tier?
The images are from steamcdn-a.akamaihd.net, which I assume is already being hosted by a third-party (Steam)
I'd rather not involve Microsoft but I recognize there are other options. It is additional work/complexity I'll probably have to take on.