I’ve been playing Russia in treaty for as long I remember, especially against lieutenants back in old AOE:
Late-game, you can’t win face-to-face against civs with stronger units. At least, without a good horse cannon spam. 100 strelet will lose to 100 longbowmen, skirmishers, cassadors, etc. It’s just not good.
What I do is I always build at least 2-3 artillery ranges behind the front lines, and I always have at least 1 of them producing a horse cannon. And if they start coming in hard, I turn that 1 horse cannon into 5 and have another one being created.
And when they see that you’re going heavy on using heavy artillery, just insta-spam halberdiers to block them from reaching your cannons and station some cav archers to discourage cav, and to contribute to the DPS.
Then anticipate culverins and make 2-3 of your own with an unused artillery range. Use pop-effective cossacks to flank their artillery and force goons (which strelet and cav archers can fight against). Play rock-paper-scissors faster than them, and keep your DPS high with 4+ horse cannons always going. Having better artillery control is a consistent way I’ve found to stand face-to-face, since you can’t rely on OP units like with other civs. I usually keep my KD/R even at the least doing this (which is impressive, because it still means you put out more DPS than your enemy to take down their stronger units).
Otherwise, you can play bully games and abuse Russia’s insta-spam to catch their armies by surprise. Scout a lot, have villagers scattered around the map, and see what units they’re making. Build an FB and insta-spam counter units to fk them up.
Like Sun Tzu said in his Art of War, “If he is in superior strength, evade him… If he is taking his ease, give him no rest. If his forces are united, separate them. If sovereign and subject are in accord, put division between them. Attack him where he is unprepared, appear where you are not expected.” Just pick good fights and abuse insta-spam with the right units.
And cossacks are EXTREMELY pop-efficient. For 6 pop, you can have 6 cossacks (decent atk and decent hp). Other civs get 3 hussars for 6 pop. France gets 2 gendarmes for 6 pop. 6 cossacks can beat them all. Hilarious when you send 60 cossacks into their base while a little army is still pounding the wall outside. There’s just so many freakin’ horses, lol.
And take note: people react to YOU as Russia - when you send in a group of opris, everybody takes a dump in their pants and wants to spam anti-cav.
I love taking advantage of this. I prepare a horde of 40 halberdiers and 3 horse cannons, then send a 5-10 opris to raid as enemy walls get opened. They ■■■■ their paints and make 20-30 goons to counter opris (“OMG opris incoming”). Then I close in on their goons with my halberdiers inside their base, or at least push them back. They try to train skirmishers, but my horse cannons lock on them as they are created slowly (no insta-spam for you). And the game is more fair against skirmishers if you’re meleeing them. In the end, I use my boosted halberdiers (with the Arson card, +50% infantry seige damage) and horse cannons to destroy the enemy buildings. And while they are so busy worrying about those units, I used my fallen population to make quick mortars and follow up (using the Age 4 mortar card) and insta-spamming any needed counter units to keep the pressure going. Just play with their minds. I think Russia still kicks ■■■.