I don't see how that is an example of ideological reasons, or how that contradicts what I said. It seems like exactly what I was saying -- GNOME, Ubuntu and XFCE all have their own separate APIs for things. I've seen that issue posted here and on reddit so many times and I never understood why anyone considers it any more significant than all the other times a random open source project removed a deprecated API or did an incompatible version bump. Yes, I get it, it's frustrating when upstream is a moving target, but that's exactly what he's saying. You can choose to follow the moving target or you can target a platform that moves slower.
And because I have to keep saying this, that is a non-issue now anyway. XFCE supports the new app indicator protocol, and since Ubuntu dropped unity their support for it is available as a standard GNOME extension: https://extensions.gnome.org/extension/615/appindicator-supp...
Others strive to have APIs that are either compatible across DEs, or there is a way for a DE-agnostic app to feautre-detect and use it when it's available. GNOME is the only project that simply doesn't care about DE-agnostic apps, and ends up making their life more difficult than anybody else. The app indicator issue is brought up time and again, because the comments on it from the GNOME developers make their attitude crystal clear. That this particular issue has been resolved since then is not important - there have been more since, and there will inevitably be more in the future, since, again - they do not care.
If you sincerely believe that it's okay to have a single DE be a self-contained app platform with no interop, that's up to you - but do understand that this is a very debatable premise, and people who don't agree with it have very good reasons to be annoyed with GNOME.
And because I have to keep saying this, that is a non-issue now anyway. XFCE supports the new app indicator protocol, and since Ubuntu dropped unity their support for it is available as a standard GNOME extension: https://extensions.gnome.org/extension/615/appindicator-supp...