You realize that Muscovy/Russia main strenght was their manpower and goverment system which allowed their ruler to do anything and they were mostly failing against PLC untill around 1650-1700 when PLC got weakened by 50 years of wars/rebelions and its economy got rekt. Poland was more developed than Russia, it was Peter the Great reforms which put Russia ahead (with constant decline of PLC).
Muscovy and Russia always had a problematic economy. Peter's reforms grossly empowered the military government branch of the state, giving Russia the ability to project power internationally with an army and a navy. However, no one can claim that his reforms got the rest of Russia ahead. It is generally agreed that his economic reforms were superficial and/or misguided and taxing, and if anything lead to more oppressive backwardness (hello entrenched serfdom and bondage factory) that neatly set the stage for the revolution.
Of course the PLC strangled all of its potential Peters as far as the army is concerned and got what they deserved, but in any case the point was never that of who had the more "development". Muscovy and Russia would do very well early in their wars but the logistical difficulties always overwhelmed them immediately after, the reason why the peaces it signed were always borderline mediocre.
So the whole "Russia had manpower" is more like pop history - eg in the Smolensk war of the early 1600s half the Russian forces were mercenaries. Most of that so-called massive (potential??) manpower was tied up in peasant rebellions who occupied large swathes of the country every now and then, and defending the land from the the annual Crimean raids.
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That being said obviously I can't agree with the present state of Lithuania. Ruthenia having pre Mongol invasion levels of development is historically unjustified. The King
Cotton Chernozem mentality doesn't justify it either. Productivity means little when there's no infrastructure in place, no roads to sell the produce, irrigation, availability of proper tillage tools etc.
Lithuania got buffed in AoW along with the ROTW so that those regions wouldn't make for a frustrating experience. Then Poland couldn't keep it under a PU so Poland got buffed in a following patch. The problem is exactly those design choices that are based on bad game mechanics (development = success) and half baked historicity. Eg the Teutonic order was not exactly a pushover for Poland. They only managed to bring it into the fold because of its internal disintegration. The game just throws development to the problem.
Then the Teutonic Order had many forts, but forts are very expensive in game, so let's give ahistorical development to ingame Prussia so that TEU can maintain its historical forts, because, well,
logic flavour. And yet despite the tedium, Poland still incorporates that land of plenty faster than history, and then you have things like the PLC wrecking the HRE and the Ottomans.
TBH things like that need sitting in the deisgn room and are beyond minor tweaks.