I mean in modern days, Germany is an extremely powerful country in the form of trade, politics, and all that but Austria and Hungary aren't nearly as powerful. If they both had war guilt and an obligation for reparations, why isn't Austria a big diplomatic player like Germany is?
In short: Germany lost 13% of her pre-war territory (principally West Prussia, Posen, Upper Silesia, and Alsace-Lorraine) but more or less maintained her capacity to function as a Great Power. Yes she lost the massive production in Saarland to France temporarily but she was still a (mostly) united, sizable, industrious state who essentially only had to overcome her own financial woes from their overspending in the war. Austria-Hungary however was completely broken up -- completely. The Kingdom of Hungary lost 70% of its territory (principally to Rumania, Czechoslovakia, and Croatia) and 65% of its population. Austria would lose Tyrol and Trieste to Italy, all of Bohemia to Czehcoslovakia, Galicia to Poland, and strips of land to Yugoslavia. This is a more detailed map.
To be more short: Germany was a pretty ethnically homogenous state and there was no real reason to break them apart much in terms of ethnic lines outside of West Prussia/Posnen which were majority Polish. Austria-Hungary was a poly-ethnic empire which even before the war (and arguably the major reason Austria-Hungary started the war) the Serbs, Croats, Bosnians, and Slovenes (the latter 3 all being under the Austro-Hungarian rule and the former being the one who they invaded) had popular support for a pan-Slavic "Great Serbia" encompassing all four nation-states (which would be realized and become Yugoslavia in 1918). The Dual Monarchy of Austria and Hungary as well was broken up and they were made into independent entities. So there was ethnic and political justification to break up the Austro-Hungarian Empire and by breaking it up they essentially neutered the power of those within -- particularly the two former leaders.
Austria would spend 20 years independent before being sucked into Germany and that was brief as after the war they were released again...and then spent to this day a separate entity from the German people and a similar story for Hungary.
TL;DR: Austria and Hungary controlled a massive poly-ethnic empire and it was broken up to fit more along ethnic lines after the war. Since then they were frankly too small to be of any great importance on the world stage especially considering both of them are landlocked and surrounded by greater powers.
