Thematically, some of them have abilities that play well with other cats, like lifegain and +1/+1 counters, while other legendary cats are off doing their own thing
There's actually a crazy amount of Vehicles now, so you very much can make a Gruul deck that's just fun mana dorks and Dwarves and Vehicles
Enchanted Cards (Rainbow Hexagon) Once the pinnacle of the game, Enchanted cards remain a cornerstone of Lorcana collecting
Im not sure that anything has
Then again, combat damage isnt the most important thing for a lot of decks, so maybe not
Other possible upgrades include things that trigger when you draw or discard a card, like Glint-Horn Buccaneer, Rielle, the Everwise, and Chasm Skulker