Half of the grand fleet is literally atleast Dc3 (Do flamingo 3rd Commander) level. Crocodile is relative to sanji in strength. the cross guild don't got enough. they literally got don chinjao for God sake. who at most is relative to doflamingo in strength if not mid diffing doflamingo. remember that he held his own against Garp in his prime, there are people like Bartolomeo who is probably G3+G2 Luffy level (rooftop). and don't forget cavendish who in dressrosa is Dc1 (do flamingo 1st commander) level. and tf is croccodile gonna do when there is people like sanji who exist. and for mihawk. zoro+Luffy would do but zoro's pride wont allow Luffy to join in. the cross guild has a few members. + some henchman but that's it
Look Luffy wouldve lost against don chinjao if he hadn't sharpened his head, it was more don chinjao forefeiting. it took Luffy to use G2 + G3 to even stand a chance against don chinjao when his head wasn't sharpened. and if his head was already sharpened Luffy would died in many instances.