First thing I noticed, Sole.
You had a lot of opportunities to charge sphere, but you didn't. Against pretty much everyone in the cast but maybe Falco, Fox, and Wolf (and even then you should charge it sometimes), you should always keep a sphere charged. ROB's reflector is too slow and punishable to be used regularly without serious risk. In all honesty, the only time you SHOULDN'T be charging your sphere if you don't have one is if ROB is up in the air above you, which means you should be out there juggling him(and even then if he's high enough where it won't matter, you should charge a spurt or two). Hilariously, I noticed that you often did the exact opposite of this, and a few times when ROB was high in the air, you ran away to charge the sphere or attempt to camp.
Second thing I noticed. You don't jab, ftilt, fsmash, grab, or full charge Aura Sphere nearly enough. I know ftilt isn't exactly useful in the matchup, but it feels like you're the kind of Lucario who still fights every character the same way, which means that you probably lack these in other matches too. Obviously you're also not using Uair enough in this matchup.
Third thing I noticed. Don't jump into the ****. You're out here spamming Fair like Rambo and somehow thinking that it'll just turn out all right. You're always moving into your opponent at all times. Even when you're airdodging, you try to airdodge THROUGH your opponent even if there is a ton of stage left to move to! You even land with fair a few times. That's a huge no-no. A lot of the times you spammed fair, you could've been doing other things, like fsmashing or ftilting or jabbing or dtilting or shooting a fully charged aura sphere or grabbing.
Fourth thing I noticed. Your airdodges are also REALLY predictable. Quite a few times you airdodge in places you shouldn't even airdodge in. A dair would've both protected you and dealt damage to your opponent at the same time if you just used it instead of airdodging. Luc's Dair is good and beats out a lot of ROB's things. You got punished so badly for this. There were a few times you could've been saved if you just did a Bair instead of an airdodge too. (Also remember Bair has very little landing lag)
Fifth thing I noticed. Your DI sucks. You should really work on that. Either mess around with special DI training with a friend, or just try to keep it in mind for later. Either way it'll come with experience.
Last thing I noticed, you went about the matchup entirely the wrong way. ROB is supposed to be a juggle-fest for you. Your job as a Lucario main is to get him up in the air above you and to keep him there. ROB has virtually no options to cover his underside, and he can't even fastfall past you reliably due to not only having absolutely no reliable coverage below him, but also because he is one of the very few characters who is actually arguably FLOATIER than we are! (exactly the same fall speed, fastfall speed, fastfall acceleration, but we have much better air speed and mobility). This means that our uair can pretty much destroy ROB all by itself, along with a little help from Utilt, Uthrow and Dthrow, and maybe even a little dtilt here and there. ROB kills us with Nair and edgeguarding. You were really open a lot of the time for both. Because you spammed aggro on him without thinking, and whenever you did camp, you did so improperly, you were constantly smacked by ROB's superior defensive options and slammed straight into that Nair and Bair a lot. Consider ROB as a character and think about how to beat him before rushing in mindlessly. His Dair and Bair are slow, and he falls very slowly combined with a very long airdodge, but he has worse horizontal air speed in all aspects than us, so using Uair from below to either hit him or bait an airdodge for another aerial (maybe another uair) is definitely a great strategy that should be used often against him. ROB has great defense, but that defense mainly comes from his spacing tilts and fair. If you use more shieldgrabs and dashing shieldgrabs, you can throw him exactly where you want him: Up (not left or right like you were doing). During his up B, ROB can Fair, Nair, and even Bair and Uair, but he can not air dodge. This means you have absolutely no risk if you throw a charged aura sphere, bair, or dair at ROB while he is recovering with that move, and there is a huge chance to hit him. ROB's grabs are okay, but they have average range, and they can only kill very late with good DI (upwards if f/bthrow, away from ROB if uthrow). Because of this, if ROB grabs you, you you should always start off DI'ing upwards immediately unless you see the startup of Uthrow, which is long enough to tell you to DI away. ROB has 3 ways to reliably kill you from onstage: Nair, Bair, and Fsmash. 2 of them require him to be in the air, and all 3 of them have a very long start up, enough to tell you that they're coming. If you watch out for them and make sure not to put yourself in too much lag when he is in an opportunity to use these, you will not die for a long, long time. Also, use more Fully Charged Aura Sphere.
tl;dr use more charged aura spheres, jab, grab, fsmash more, don't jump into the ****, airdodge better, work on your DI, learn to treat ROB like ROB, and spam more uair because ROB sucks against juggles.
