I don't think the kukui team had any intention of being part of the cast outside incineroar, it was more of a last wall, yes, I think it's okay.Korrina's Lucario essentially dragged things out with a long *** 5-episode arc with weird aesops where the whole group was reduced to Korrina's cheerleaders rather than letting Ash get his own Lucario with a Lucarionite (hence why Ash-Greninja had to exist). And in the end, it turned out that mastering Mega Evolution made it easier to defeat in eeeeeeeeeeeeevery appearance it got that was a normal battle. Gave me worse vibes than the losses Ash got through Ash-Greninja (in fact, they're almost alike, it's creepy). In a way, this arc was a worse version of Maylene's arc, where Dawn had a good lasting impression on Maylene next to Ash, but Korrina's arc made the horrible mistake of adding TRio in...pretty much all the big moments (rather than Ash or anyone else making breakthroughs directly) that led to Korrina finally getting through her Lucario.
Kukui's Lucario was...odd, but that was mostly because Kukui was the only person in the entire region who couldn't bother to do Ohana properly with his team while everyone else did. Maybe the writers weren't ready to have a Lucario for over 100 episodes of exposure? Who knows, but his was just an odd addition because Gladion couldn't have it around (as his in-game team has it) next to his imported Dusk Lycanroc (because edge) and last minute addition Zoroark. (I'm also put off by how Silvally was second fiddle to Dusk Lycanroc, but that's a different story).
As for Gladion, I think his pokemon had good screen time, Silvali in the past and his relationship with Lili Lyncarod, being a representative of his rivalry with Ash and Zoroark had the most battles, contributing to the mystery, Monh and with Magearna, apart from that, Silvali was not the strongest pokemon.