I like xmpp, but it is not a discord alternative. It is a WhatsApp / Signal / iMessage alternative. It doesn’t have 80% of discord features, I use discord a lot and I don’t have a single group chat.

which features are missing from xmpp that are necessary for most gamer groups? is it the protocol that is missing the support, or specific implementations? genuinely asking since I’d been considering setting up an xmpp server for my gaming groups

Do you use features like permissions, channels, threads, bots, … a lot ? Application using xmpp as a backend are great and can be all you need if you just want a simple voice/text chat with no additional features. There is no equivalent to most “server/community” features of discord in the xmpp protocol, and it is something that needs to be implemented at that level for it to work.