Interesting, via iOS safari the page was quick to load and scrolled smoothly, no noticeable performance issue (excepting the payload size is excessive).
Worked fine for me on AOSP8 with Iceweasel on Honor 9 too, albeit on ac wireless with 400Mbps connection (at least I didn't notice any slowdowns, and this is hardly top of the line hw or sw).
Ouch ouch ouch ouch ouch. Flagged the submission for this reason, it’s going to cause severe problems for lots of people, and being GIFs and so enormous they don’t even load well (when I start loading even the first GIF by itself, it spends a lot of its time loading at below one frame per second). The GIFs should be removed urgently and replaced with static images and links to videos.