>>jayden+(OP)
Thank you for writing this post! I opened youtube a few days ago to this as well. On a 24" 1440p monitor its ridiculous. It's incomprehensible there's a UI/UX team that gets paid millions of dollars per year and the result is changes like this. Thank you again for writing this post. After searching it seems like they've been "testing" this in segments for a while now.
As a result I installed the "Control Panel for Youtube" chrome plugin and Im able to fix it back to 6 videos per row. I also found I could make shorts play in the traditional youtube player by default - which is an added relief.