I'm not sure this series does the "emotional factor" right because Ash is extremely static, and any other attempt usually has a very silly explanation as to why the drama happens at all or how the drama was...really never there but was a fake out.
Remember, Alain was an extremely normal lab assistant going on a(n aimless) journey until some lion-maned adult beat him in the woods and utterly manipulated the hell out of him with the least effort.
Whatever beef or tension Ash had with Bea was anti-climatically resolved as soon as they tied. Afterwards, it was sunshine and rainbows (more so when it turned out Korrina was actually a fan of Bea for getting majorly screwed).
I can't say anything about Raihan's story because it's more barebones than in the games.
This is exactly the main problem with Journeys, there is little to no connection in most of Ash's battles, and the very few with some sort of emotional connection of development, are controversial battles.
Ash vs Iris has obviously their meeting again and Dragonite learning Draco Meteor, but the way Ash won is very controversial and doesn't help to make this battle memorable.
Ash vs Bea is the only "good" rivalry of the series...and their last battle was not that great either, and imo it was way too early in the series.
Ash vs Raihan where both are Leon's rivals lacked some sort of proper story about Raihan or proper interactions between both characters.
And we can continue. The main problem of those battles was not exactly how visually good or bad they were, is the lack of a proper story that makes those battles to be remembered in comparison to your average visually good battles.
What-could-have been is not an argument, since Ash's relationship with Alain was superficial at best prior to TF, in a similar sense to what his relation to Raihan was during their battle. There was no deep connection there, but the former was still presented in a manner that was visually appealing. THAT was a factor as to why it was so popular, along with the fact that it was Ash's first League final (and the hypebait about him winning). Not because of his connection to Alain.
Again, how does that justify and excuse the bad production and mismanagement for other important episodes? Unless you slipped up and ironically implied that there was a higher priority for this one? Are you saying this episode is far more important (regardless of a setup in the past series) than the episodes pertaining to the current main cast?
First, as other people and I said, this episode was potentially planned since SM's last year knowing Journeys premise, this makes it way different in how much time you have to plan something in comparison to any other character return.
And second, this episode is the conclusion of a Main Character's story and arc. It is not comparable to any other Journeys episode.