Regarding the qeustion of 'when did Poland become a protectorate of Russia' (@Felix), this was essentially defacto established in 1710 after Poland's conclusion of the Great Northern War. It had entered the war in a fairly good position (ie, balanced coalition between her and Russia), but after failing and then having a civil war during this time, and Russia realizing it's military power as time went on, it became evident that Poland's ability to support any action against the Swedes became fully dependant on Russia. Henceforth, politically and militarily, she became marginalized as a country, and Russia 'offered' to enter into a protective alliance as part of the Grand Sejm's treaty of 1710.
Regarding the question of Nobles in Poland. While it's not easy to validate the hypothesis, one can deduct key elements contributing to the lack of 'pride' among the nobles.
- The nobility, strangely enough, believed in Sarmatism; the idea that the original noble families of Poland originated from Sarmatia and that they settled and subjugated the local peasants (or... in other words, Poles... so the mindset of the nobility was, at best, quasi, if at all, 'patriotic'. This style of thought really came to fruition in the late 1600s and survived mostly thru all of the 1700s. If one believes their ancestors simply came to this 'land' and subjugated the local population (... the original Polanie), then does the nobility really have the elements one needs to have a sense of national pride/unity for all the people of the land? I venture to say a big 'NO'.
*There's also an old polish saying that essentially means 'every noble with a sword is his own king'... ie... they cannot be governed, they are their own little nation in person, and those without a title are nothing. If this was a prevelant way of thinking back then, one has to wonder how much did that have an effect on caring for one's nation as a whole? Problably very little.
- Poland had an outsized proportion of 'nobles' vs. general population. Of course, many were undeniably poor, but conceptually, as far as the military goes; it was they who were the only ones allowed to wield weapons in battle, and the only ones who believed they should be. In most other nations, peasants were commonly conscripted and armed... thus, across all social classes, in other nations there was a sense of defending one's nation. While in Poland the peasants were alienated from this (very few instances of peasants being part of major campaigns outside of being the ones to dig ditches/gather resources).
*This leads to the notion that the peasentry probably had a far lower sense of identity than, say, their counterparts in Russia... who were certainly consripted into military ranks and allowed/expected to fight and defend their country (as like in other nations).
- Poland was more often referred to simply by the term Commonwealth (Rzeczpospolita) among the nobles. Rarely, in hymns of that era was the term 'Poland' at all used... instead, texts, hymns, etc favored the term 'Rzeczpospolita'... A close reading of a literal translation of 'rzecz' and 'pospolita' is 'thing common'... which implies losely 'something that belong to everyone'. This, even symbolically could have had a significant effect on the idea of what it means to be Polish and having a sense of unity/pride:
There's a slight difference between the idea of a nation named after its People, and people after its nation, and the idea of using a term that simply implies these lands are common to all. The latter does not tie people to a sense of unity/identity/pride to a nationality. Hence, the mindset of nobles towards their country had a twist that could explain why it was so different from other countries, and why the nation wasn't as cohesive as other nations.
In conclusion, to explain why the nobles didn't have a sense of pride isn't necessarily rooted in simply... not liking one's nation. In fact, the nobles had a LOT of pride in the concept of how their nation governed itself. This is a paradox because 'why would anyone let things get so bad for their nation?'... but if one considers that in the late 1600s thru 1700s, the nobles didn't really think of Poland as 'Poland', and themselves as 'Polish'... but rather as descedents of Sarmatia who subjugated the people of a land that is common to all (Rzeczpospolita), then one realizes that this is exactly not for a lack of knowing what pride meant, but for a tradition where the nobles believed it was them who were the nation, and not the other way around.