How it is that you "forget" to mention the Golden Freedom?
The Golden Freedom had only one con and that was the infamous "Liberum Veto" however vetoing things was rare and even rarer was it being taken into account, in theory any noble could veto, in practice it was done rarely since it often meant death sentence after the Sejm and if it was just any noble he'd likely be ignored anyway.
Veto breaking off each Sejm is just another communist myth that stuck i'm afriad.
That any of the Commonwealth "nobles" could and did block any progress
See above, in theory any noble could block it, in practice he could not.
In the pay of the magnates who were all in the pay of the partitioning powers?
Every countrys political elite had its share of traitors of the same magnitude, polish nobility however distinguished itself in that it had much more patriots, in fact polish nobles were the only ones who willingly gave away their priveliges in favor of other classes in the constitution.
That every time the new King had to be elected (bought in reality).
Not a single king in polish history was bought, not one.
That the nobles vehemently opposed regular taxes and a standing army?
That must be why in between 1654-67 (thats 13 years) Poland maintained a standing army of 50.000 bolstered by 10.000 mercenaries and 10.000 Lithuanians, because nobles vehemently opposed regular taxes!
Also polish armies were much much more expensive then Western ones due to being 80% cavalry so Poland maintains an army that'd cost as much as 100.000+ equivalent in Austria or France.
Yes plenty of nobles did stray from ideal citizens but the notion that Poland fell because of its nobles is nothing but a communist myth.
Polish nobility was for a very very long time the most enlightened, well educated and patriotic in Europe, its martial skills were for centuries the best in the world, the polish noble not only regularly defeated the best of Europe in defence of Poland but didnt hesitate to pay in money or blood.
Even when Poland fell from grace and the nation with it it was the nobles who revived the nations spirit, the nobles who came up with constitution and begun a work of healing and restoring the country that was un-f*cking-paralelled in the world.
In no country in the world outside Poland did nobility just get up off its arse and decided "this country is going down if we dont change, lets surrender our priveliged position and rebuild our country to our former glory together with citizens and peasants as equals."
That happened only
in Poland, other countries needed another century to come up with something like that so polish nobility despite all its flaws is a thing to be proud of rather then spit at.