If Austria was humiliated, it was because it kept joining anti-French coalitions and getting beaten.
I don't mean battlefield defeats (which they certainly
were humiliating but off topic) but at the terms Napoleon put on them.
Tarylland wanted to let them off easy after the war of the Third Coalition since he viewed the, as a buffer against Russia. The Austrians by the 1780s no longer trusted the British. They were antagonistic towards the Prussians and Ottomans. They distrusted the Russians. While the Holy Roman Empire was de facto a series of related kingdoms and duchies rather than a nation, its facade was good to keep the population of Germany (Rhineland? I'm specifically referring to geographical region since the nation obviously didn't exist yet). With the Austrians getting mercy terms, Tarylland thought Napoleon could peacefully turn Western and Central Europe into a Bonaparte hegemony.
Because they were left smarting, the Austrians kept going for these coalitions. And in the second one they didn't do anything of note. You got it backwards, it is the humiliation at the end of the war of the third coalition that caused them to keep joining more even though most of France enemies (besides Britain) stayed out until the last one or whenever Napoleon did something to bug them (in the case of Spain put his brother on the throne). They knew that they might face Prussia and Russia in separate conflicts one day off in the future, but getting rid of Napoleon allowed them a few decades of prosperity.
Look at this from the king of Spain's point of view. France treats the Netherlands like shit. The new grand duchy of Warsaw is a clever way to disguise stealing of the area's wealth (1/8 of the taxes went straight to France). Austria, which could have proven useful to Napoleon, was humiliated. Napoleon keeps sprouting the ideals of the Revolution as rhetoric in public long after he became Emperor. The same revolution which killed the Spanish king's cousin! If I sent the King of Saxony in 1910 back in time to talk to Spain not about the future but about what he did as King of Saxony, the Spanish king would think the latter was just a glorified duke or marquess. Which, he was. The king of Spain could have been fearful of being reduced Napoleon's glorified duke who is called king.
Also, plenty of Spanish nobles thought Spain was trying to wrest away from France and go into neutrality. They must have gotten the idea from somewhere and rumors can be true you know...