That guy was talking about the WWI and I'm pretty much sure it was after 1821, if my terrible books are not wrong. Also, I don't care about Ottoman tech group being defeatable but we both know Russians are a bit overpowered with their doomstacks and that's what I'm talking about.
I don't agree at all and I really don't understand the sentiment. As stated before, there're definitely nations having issues with Russia (e.g. Manchu, Ming, Hordes), but that's not because it's Russia, it's because they have crappy units and tech groups. If 100k Frenchmen would get to Ming, they would beat them up just as well as 300k Russians - it just doesn't happen because Russia has a land connection and French does not.
Anyway, especially as the Ottomans you shouldn't be having any serious problems with Russia whatsoever. You get a nice 10% discipline, you have +30% morale if you go pious and you get the Ghazi NI. Overall that gives you stronger armies (until mid-late game if you're not westernized) and about the same potential manpower. I really don't see a problem at all with Russia if you're playing the Ottomans (or any other major tbh).