Openly acknowledging I'm a Lucario main before I post this. (SO BIASED)
I think the reason why Lucario is so hard to place on a tier list is because he has a super polarizing matchup spread. At a high level, he should body certain characters (Ganon, Dedede, Falcon, Charizard), but he also loses to a decent chunk of the cast. Here's who I personally think Lucario loses to, obviously I'm open to discussing it:
Out of those characters, here are the characters he gets BODIED by.
- No answer to shine pressure, stands during waveshines, combos Lucario hard, one of the characters who can very effectively edgeguard Lucario.
- Falco obviously combos the **** out of Lucario, and if a Falco knows the matchup, they should just sit, laser camp to bait Lucario approaches, punish hard. Can also edgeguard Lucario well.
- Wins the neutral every time, even if Lucario has aura. Can nair out of Lucario's combos at decently high percentages, outranges Lucario. Very hard to combo. Nair destroys Lucario.
- Literally cannot be combod by Lucario. Crouch cancel dsmash/nair end any combos that Lucario could potentially start, and he can combo the **** out of Lucario.
- Destroys Lucario in neutral with fireballs, combos him hard, can also nair out of combos to a lesser degree, CC dsmash eats Lucario, and between cape and bair, he can also edgeguard Lucario effectively.
- CC dtilt and one frame upB to escape any combo, while being able to combo Lucario up and down the stage? He can bucket Lucario's only projectile safely? His hitboxes stay out longer than a desperate college kid at a frat party, preventing any sort of approach from Lucario? Why did I make this explanation in question form?
- You'll notice most of the floaties have a nair that can escape any combo effectively. Peach wins the neutral, she's hard to combo, turnips are solid for edgeguards, combos Lucario hard.
All of these characters are imo at least 65-35 against Lucario when the players know the matchup. Lucario can't deal with floaties, disjoints, or good shield pressure, and especially can't deal with characters with good crouch cancel options or low-frame nairs.
Personally, I would make an argument that Lucario's neutral game is very below average WITHOUT aura, but when he has aura, which I've estimated occurs about 11 times a game (assuming Lucario deals 400%, 100% in shield damage, and starts with one aura), his neutral becomes top five in the game. However, 11 times is not that many aura charges, and if you consider that he's also spending it on recovery, combos, and aura bombs, you realize that he doesn't have the aura advantage in neutral all that often.
I just find it hard to believe that a character with that many negative matchups is a top tier character. I believe he destroys some characters, but also loses to enough characters (many of which are in the high tier) to keep him from being the top tier character some of y'all think he is.