It’s nothing like that. You can already trade currencies between players. This just means that you can buy someone’s listed offer with one click instead of whispering 100 people hoping someone will respond and trade with you. Players have been asking for a feature like this for a long time and the announcement has been received extremely positively.
Plus, they’re only adding it to the next temporary league (which is like a season). They said the Q&A that the intention is to keep it afterwards but if it for some reason completely fucks up the economy they still have an out.
I’ve never used Twitter a lot and I’ve mostly stopped using it, but Mastodon is just not a viable alternative for most people. I used Twitter to keep up with things. I made a Mastodon account like two years ago, but almost none of the people or organisations I care about are on there. And most of the ones that are on it aren’t posting. So I’m basically never using it. The same is true for Bluesky. Threads may be better but I’d rather avoid anything from Facebook.