head to head
Sea of Thieves asks more than Command & Conquer: Red Alert 3, and the gap is variance.

Reads · Grand Arena
Three-faction Cold-War RTS with naval combat where faction asymmetry and multi-front pressure are the core tests.

Reads · Competitive PvP
Open-world pirate game with PvPvE ship combat.
Command & Conquer: Red Alert 3 leans Reads (Grand Arena); Sea of Thieves leans Reads (Competitive PvP).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Command & Conquer: Red Alert 3
Naval and air micro alongside base-building taxes player bandwidth
Sea of Thieves
Ship sailing and naval gunnery require hands
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Command & Conquer: Red Alert 3
Three-faction asymmetry means opponent choices must be constantly predicted
Sea of Thieves
PvP ship fights are pure mind games
Sea of Thieves leans clearly harder on variance.
Command & Conquer: Red Alert 3
Ore spawning and naval choke variance add moderate uncertainty
Sea of Thieves
Server encounters, weather, loot vary
Command & Conquer: Red Alert 3 leans a little harder on optimization, though the gap is small.
Command & Conquer: Red Alert 3
Production order and defensive placement are learnable but more flexible
Sea of Thieves
Routes, loadouts, ship setups solvable
A matching score does not mean a matching test. Two games can both sit at 10 on execution and demand completely different things of you - which is why the reasoning above matters more than the number beside it.