I'm a bit confused. I talk about the 16th century Empire and how it was doing, and you cite the 17th Century Dutch Republic. Wouldn't 16th Century France's fiscal administration be the more valuable analogy? You keep equating "more centralized than thought" with "Dutch Republic fiscal system."
It's not like France didn't have trouble raising money and had a messy tax system...
No. I keep equating "centralized" with "a state actually capable of acquiring revenue".
1579 and 1599 are not the 17th century.
And the Dutch Republic's fiscal system is a reason for the Dutch being rich, not a guarantee of obedient tax payers.
But if you want a French example: 1596 revenue is 31 million livres = ~21.7 German florins by Wilson's conversion table.
From a population roughly equal to the nonHabsburg part of the HRE, with France currently "a country severely weakened by civil war, brigandage, high prices, and interrupted trade and agriculture, and its fiscal system was in pieces".
Despite that, it's producing as much revenue (4/5ths assigned and alienated, yes) as the Reichstag gave in the 1590s (you didn't specify it being per year, so I'm assuming that's over the course of that period).
Yeah, the HRE is a disappointing mess, even if Space Oddity is right about absolutism.
I should note that I'm not saying the HRE couldn't have done better - it certainly had a chance earlier and it might have had one in this period - but what happened OTL is pretty consistent with a very loose confederation.