Ottoman troops are good likely because of the Janissaries giving a massive boost to discipline (but the Janissaries are a temporary buff), not because of Ottoman troops themselves.
As for the Ottoman troops, yes, they are good in 1500-1600, but Ottoman units decline rapidly in quality while Eastern troops rapidly increase in quality.
Again, Russia should not be expanding into China/India, and yet they can easily do so.
Ottoman NIs are stability oriented, not combat oriented. Their meager military bonuses get trounced by Russian +125% Manpower, -50% infantry Cost, +50% Land Force Limits.