Display MoreThreads with multiple YouTube embeds put a lot of strain on devices and make pages load slowly. Many times I need to escape the massive loading by just going back to the previous browser location. It's even more responsive to either close the AKP tab or force quit the browser altogether. It's a poor user experience.
Here's an example thread with poor loading performance: Kpop songs about rain
Here's a solution to a similar issue that someone has posted that includes a demo: https://css-tricks.com/lazy-load-embedded-youtube-videos/.
There might even be a solution officially provided by YouTube itself.
This would be easy to do if not for the fact that this is aftermarket forum software that you cannot access the actual code base for and needs to be modified properly with (also aftermarket) plugins only. Thanks though - I understand the issue