And yet their build system is still the same as it pretty much has always been. There is no easy way to sustain any sort of development energy with a developer unfriendly system like that one.

LibreOffice realised this early on and did the hard yards to fix fundamental issues like the crappy build system, and to put into place developer friendly infrastructure like gerrit. The OpenOffice team didn't see this as important or even necessary, and now they are withering on the vine, but complaining about it quite a lot.

That Symphony code can only take you so far. That was integrated several years ago. What have they done since then?