Supreme Commander: Forged Alliance with the LOUD mod is the greatest RTS ever created. Nothing modern gets even close to the level of detail and scale this game has. 10s of thousands of units all with real projectiles can than be dodged.
Get some friends together or play by yourself. Up to 16 players in a match.
Awesome AI with lots of configuration so Co-Op play is actually fun, you can tune the AI easily to present a challenge but still not get wrecked instantly.
Skip subcom 2 tho that shit's trash...
Buy it on Steam: https://store.steampowered.com/app/9420/Supreme_Commander_Forged_Alliance/
Install the Loud Project: https://www.moddb.com/mods/loud-ai-supreme-commander-forged-alliance
Download and test out the player made maps via the Loud Launcher.
You're quite welcome!