I’m going to try and look at it a bit differently
Disclaimer it’s my opinion lol not saying anything is facts
Lucario has been the perfect Ash Pokémon since the Lucario movie (it’s debut)
Not just because of the movie (is a big factor)
But a Pokémon that’s strong but not Pseudo Legendary strong giving it a good balance of reliable but not unbeatable
It’s a friendship evolution and one of the best things about Ash is his bonds with people and Pokémon
It’s a fighting type, Ash I think more than any other type (only argument I can see is fire) is so similar to the fighting type from personality to battle style
Aura, it can feel a bit like the chosen one but I think since the movie it has been handled in a good way where Ash isn’t some super hero or chosen one but just something inherent about him (kinda like Iris with dragons)
And Lucario’s aura connection makes them a good match
Just as a Pokémon it’s the perfect match imo
And now specifically about Ash’s Lucario
Again my opinion I don’t really want to get into Journeys with screen time and such
I think personality wise it’s a near perfect Pokémon for Ash, it’s an appropriate mix of the cool Sceptile, the eager to battle Charizard, the emotion of Infernape, the internal motivation of Greninja, the pride of Incineroar and so on making it the amalgamation of his aces
Which pairs well with Ash as I think the best Pokémon for Ash are the ones likeminded to him which is why Pokémon like Pikachu Greninja and even Pokémon like Swellow work so well with him
It doesn’t feel forced (to me I know others disagree)
Outside of the idea that since Journeys isn’t doing pure Gen 8, giving Ash a Lucario is one of the more natural and interesting decisions
Having a mysterious egg that only responded to Ash builds upon the aura connection and still gives some of the egg pokemon traits that Pokémon like Phanphy, Scraggy, and Noibat had with Ash
You can argue that Ash just so happened to be in the area as a random egg but I feel that logic goes for nearly all his Pokémon, (he so happens to find a special Froakie, he stumbles upon a stubborn Taillow, came across a Litten before a bad time in its life etc)
And honestly I prefer this way over him finding a random Riolu or Lucario in the wild especially at this point after all the Riolu and a Lucario seen in the anime, as this Pokémon truly feels like his
The aura connection sync bond thing also felt very natural to me mostly due to all the prior stuff like Ash’s experience with it and Lucario’s having the natural connection with Aura so with this unique combination that Ash and his Lucario have, this Aura connection is similar to the bond phenomenon but gives Lucario something unique and a power up yet not “fanfictiony” like Ash-Greninja (don’t hate it btw just pointing out that “Ash”-Greninja sounds like a fanfiction thing lol)
And I’m not going to argue about Journeys here as I’ll get off topic but I really like the bond and personality that Riolu/Lucario showed since it’s debut
It was just so eager to get stronger and prove itself and had so much natural talent mixed in with a lot of potential
And it grew into a Pokémon that had a bit more pride which showed multiple times
And it got to the point where it put its pride to the side to work with Ash and surpass its limits
And possibly become Ash’s strongest Pokémon
So I think Ash’s Lucario hits the right mix of being the perfect literal Pokémon for Ash, personality wise it’s near perfect for Ash, it has the underdog quality of not being like a Garchomp or Metagross or a Legendary but also has insane potential with the Aura Sync Boost and Mega evolution
(Combining qualities from Pikachu and Greninja is the simple way to say)
So yes Lucario is the ultimate ace to me
Due to Journeys mixed reception Pokémon like Charizard and Greninja might get the nod from most fans because of less turmoil around the series but I think Lucario has made the case to being the Ultimate Ace