So just speaking from my personal experience, XMPP was absolutely useless for me, whereas OpenOffice wasn't. Microsoft did succeed in preventing OO from eating significantly into its market share, but OO continued to exist and be useful. It eventually caught up on the ability to read and write MS Office XML files, and in the meantime I only had a few occasions where I had to tell people "I can't read docx, send it to me as doc or rtf". To be fair though, I'm not a super heavy user of Office software.
In contrast, XMPP was basically nothing without Google. I couldn't use it before Google federated, and I couldn't use it after Google defederated. ¯\(ツ)/¯
Kbin/lemmy/mastodon are in a far better bargaining position than XMPP was, and in a better position than OO as well. They're perfectly usable without being connected to corporate platforms, and they don't need to market to corporate customers either. To be clear, I'm not saying that they should or shouldn't block the corporate platforms. I think it's actually probably best if some of them do and some of them don't.