Pachirisu wasn’t included in Se Jun’s team for the novelty of it, or because he wanted to prove things to people. When you think of attention support, the first names that come to mind are Clefable and Amoonguss, but he put more though into it and noticed that a often neglected Pokémon actually had what it takes to fulfil that role better in his team, in virtue of its typing, movepool and ability. If there was another Pokémon that could do that better, he wouldn’t have used Pachirisu. And that is amazing, because he discovered a way to differentiate the squirrel from its competition, which will award it with higher usage. Such cleverness awarded him with the Champion title.
But we can learn something of it other than a Pachirisu moveset. It teaches us to look deeper when building teams. Your Amoonguss is being worn out by your own Garchomp’s Earthquake? Maybe you could give Carnivine a try. Did you know that Volbeat and Illumise can use Prankster Encore, and Illumise can use priority Wish to pass HP before fainting? Maybe your Mega Charizard Y would take special hits better with the aid of Cherrim’s Flower Gift. Sure, these Pokémon are NU for a reason, but they’re all names to remember. Maybe your team is just the right place for them?