Even though Monkey D. Luffy has attained a new form, Gear 5, and has mastered all kinds of Haki in One Piece, Shanks is still a step ahead.
Even Gear 5 Luffy is Not Strong Enough to Beat the Man Who Inspired Him to be a Pirate in One Piece
One Piece: 5 Conqueror Haki Users Who Are Still Far More Powerful Than Gear 5 Luffy
What is you exact thought on Gear 5 and why? : r/OnePiece
SPOILERS: Will the awakening be enough for Luffy to beat Kaido, especially after seeing Kaido one-shot Luffy with his haki imbued seastone club? - Quora
One Piece: 5 Terrifyingly Strong Characters Who Can Beat Luffy Even in His Gear 5 Form
Are Luffy's Gears Inspired By His Past Adventures ? : r/OnePiece
One Piece: All resemblance between Luffy Gear 5 and Sun Wukong - Spiel Anime
One Piece: Why is Gear 5 so important? - Dexerto
Will Luffy learn Gear 5 against Kaido? - Quora