As far as the mainstream Pokemon titles are concerned, Pokemon Legends: Arceus is arguably one of the more unusual takes that Game Freak has rolled out in recent years. Now, I am fundamentally aware that PLA isn't technically canon, but it resembles the 'standard' Pokemon formula enough to make the latter a fair benchmark for comparison. But with the game.
There are many ways for players to gain EXP fast in Pokemon Brilliant Diamond and Shining Pearl aside from battling wild Pokemon and Trainers. These methods involve on several holdable and Key Items, as well as partnering several NPCs.
Pokemon Brilliant Diamond and Shining Pearl remake the original Diamond and Pearl for the Nintendo Switch. They're still lengthy, fun Pokemon adventures, but not much has been added, and even the remade graphics are showing their age.