For long-term appeal, Pikachu, Mew, and Eevee-related cards continue attracting strong demand from collectors worldwide.
There are some pretty chonky flyers in the decks too, with Brainstealer Dragon being at once a great card for the exile-and-play-opponents-cards archetypes, but also a great fit for reanimator decks that want to steal other players stuff
Tactical retreat
Wrath of the Skies misses Kappa Cannoneer in most cases, but a manaless Solitude makes it easier to pay the ward
These have all held their price points fairly well given their relevance in Standard and Commander--they come into play untapped and are fairly easy to "turn on" so that they can tap for both colors of mana
Making a Frog mostly unblockable might not help Kenrith, but if I've got Yargle and Multani, or just Yargle, Glutton of Urborg, in play, I will be well positioned to put some pressure on a tablemate's life total