I am trying to make a 2024 version of my paladin. I can pick Oath of Devotion because it is free. I can pick the Xanathar's options and Oathebreaker because they are from 2014 content I own, but I cannot pick the 2014 version of things I own if they're in 2024 content I don't own. I can't use the Oath of the Ancients.
After doing some quick searching it looks like they're only not selling it anymore and didn't actually remove anything. https://www.dndbeyond.com/posts/1201-faq-for-mordenkainen-presents-monsters-of-the#faq01
This tracks with my experience. I haven't lost access to anything frim Volo's. Here's a screencap of using Volo's version of Kobold and one of a monster stat block from it. From before I showed a screen cap of the lore still being available. I'm not sure what people are upset about, maybe theyre just confused and think people that bought it lost access to it?
There are legitimate things to complain about with regards to Beyond, but I don't think this is one of them.