I don't know who Luffy is but Ranma can do/should be able to do piercing and cutting techniques. Ranma goes to pretty extremes on occasion to avoid seriously hurting his opponents (hell he saved several of them like Herb preventing them from getting seriously hurt) but Ranma has seen a lot of those types of techniques such as Ryoga's belt or bandannas, Kuno's pressure waves, Ryu's and his dad's Vacuum blades, Kiima's feathers, Herb's ki blades, Konatsu's cutting paper storm, etc. Given what we have seen Ranma do (like learn the Umisenken after seeing it only once or altering techniques mid-battle like the Hiryu Shoten Ha that froze and sliced up Saffron) he should be able to do several of those types of techniques were he actually trying to seriously hurt his opponent (which the only opponent he ever tried to actually seriously hurt was Saffron and that was after he ran out of other options). The thing is Ranma rarely takes the battles he is in seriously (for example he was ignoring Kuno to look at the pictures or how he was arguing with Akane during almost the entire first battle versus Ryoga) and doesn't want to really hurt his opponents which is why we see his opponents who do want to hurt him or at least find that as acceptable using slicing techniques and Ranma not using them.
Most of his battles aren't even to beat the opponent so much as to beat them at their style or beat their technique (Hinako he could have just knocked out whenever he wanted rather than try to beat her technique, martial arts cheerleading limited himself to the styles rules trying to beat her at her own game, etc.) Even against Saffron he didn't get serious until he was running out of options (at which point he went for maiming rather than killing since he could have cut off Saffron's head rather than his wing). We've even seen Ranma use slicing techniques just not against people (other than Saffron) he cut out a perfect circle at Ryoga's house, he casually sliced through a rope that the principal was on, etc. that isn't even counting the Nekoken which casually cuts through basically anything.
A Ranma who is in a situation in which he views killing or maiming his opponent is an acceptable outcome (very rarely) fights a lot different than a Ranma who's goal is to defeat a technique or style. Also given or finding knowledge of an opponent he will use that knowledge against them (he'll use a reaction to breasts, a curse against an opponent, or basically anything he finds to use against them finding mind altering drugs -like suggestion incense, ambush, magic items, blackmail, etc. as acceptable) or prepare by bringing weapons or armor with him (like how he had brought them to fights in which he had time to prepare such as using iron pans to block/deflect the Ashura's attacks).