If you control a commander, you may cast this spell without paying its mana cost.
Creatures you control gain indestructible until end of turn.
Flawless Maneuver is one of white's premier protection pieces, and the free cast is what makes it a staple. In Commander you almost always control your commander, so this is effectively a 0-mana board wipe insurance policy — you hold up nothing and still walk through Wrath of God, Blasphemous Act, or a combat blowout.
It shines in creature-heavy decks that fear board wipes: tokens, go-wide aggro, +1/+1 counters, voltron/Voltron-adjacent builds, and any deck investing heavily into the battlefield (Sram, Krenko, Ghave, etc.). It also enables aggressive alpha strikes since you can swing all-in, then make your team indestructible after blocks.
Caveats: it does nothing against exile, -X/-X effects, sacrifice (edicts), or bounce — and those are common in cEDH. It's also dead if your board is empty or you're light on creatures.
Don't run it in spellslinger, control, or low-creature lists. But in any white deck building a real board, the free cost makes it near-auto-include.