The two lines you mention do cut off at some points, though. The DS no longer had backwards compatibility with the GB and GBC, the DSi with the GBA, although the 3DS re-added GB and GBC, just digitally. The Wii U also doesn’t support GCN discs. All of these, however, work pretty well with homebrew like mGBA and Nintendont, they’re just not available officially.
The only (large enough) area which is currently lacking is multiplayer games, especially those with anticheats. Unfortunately, there’s nothing users can do about that other than wait for game developers to enable wine support, which, despite EAC and Battleye significantly simplifying the process, many still haven’t done.
That’s not all the context, though. GamersNexus made a video detailing it further. and a follow-up.
XMPP is a protocol for decentralised chats, allowing people registered on different servers to chat with people on other servers, kind of similar to how email works (and Lemmy of course).
Google Talk was a service by Google which started with XMPP support, letting users from other XMPP servers chat with Google Talk users. Google Talk was always slightly different from the XMPP standard, due to having proprietary code in its backend, leading to chats between Talk users working flawlessly but not between XMPP and Talk users. Slowly, Google Talk became more popular than the other servers.
Eventually, XMPP server-to-server support was removed as part of their transition to Hangouts, meaning once Talk users switched to it, XMPP users would no longer be able to chat with them and would have to switch to Hangouts. While XMPP still exists today, it’s definitely a niche nowadays, and this is part of the reason.
Edit: proper paragraphs
Yeah, I agree with that. I was just trying to point out how Nintendo’s BC has never been as complete as it could be, for whatever reason it may be, but yeah, they’ve been pretty good at guaranteeing last-gen compatibility so far. Let’s see how it goes with whatever will succeed the Switch.