For a long time, I’ve wanted reserves and continuity to be more prevalent in the anime.
I can think of dozens and dozens of episodes where Ash could have brought back a reserve to either teach one of his current generation Pokémon, help him win a battle, to show off to his current companions, etc.
^ I think, perhaps, if the anime had been written more consistently, that could have been easily accomplished.
And to be fair, up until the end of DP, there was a minimal continuity level and reserves did make infrequent appearances and/or were acknowledged.
Since then, it has just become much more rare. It just is what it is.
I think it would have been great if Journeys had a two-parter full battle where Ash battled an E4 like Flint with some of his OG powerhouses like Bulbasaur, Snorlax, Heracross, Swellow, Glalie, and Gliscor.
I don’t expect it though. None of the target audience were even alive/were just babies when those Pokémon were battling on screen. Even Ash-Greninja and the end of XYZ was 5.5 years ago.
Would it make sense if Ash’s Journey squad took down the likes Cynthia or Leon?
Probably not.
However, there’s no point worrying about power levels or reserves. If the plot demanded for Ash to win this tournament, he will with this team, whether he had reserves or not.
I’ll hope for more reserves, but don’t expect them. I just want to see some good battles and for Ash to get a respectable ending in this tournament/series.