Every trainer probably has a similar memory and is now willing to put their money where their Meowth is, in terms of buying cards as an adult they could never afford as a child
In comparison to modern eras like Sun & Moon, Diamond & Pearl's top cards (with available prices) can't compete with these modern marvels
With offspring, that's two damage, and it's easy to see where this is going - it's an alternate win condition in grindy games and its unearth ability means it can come back to provide that effect for one extra turn whenever it's most relevant
On top of this, Hakbal can also ramp you by attacking, but you do need to buff him so he'll survive combat -- which the deck also provides
Combat tricks and protection spells like Outmuscle make each attack lethal and safe
Admittedly, while the long-term cost of Summon: Yojimbo might be one mana, youre obviously paying four for it