Shifts in collector preferences, changes in the popularity of certain sets, or the release of new cards can all impact the desirability of older ones
It makes sense why this card is banned Modern and Legacy and restricted in Vintage
Molten Collapse will have to compete with Terminate for Rakdos decks in Modern, but the versatility of Molten Collapse is no joke
Overall, if you pick good themes (popular character, limited availability, strong artwork) and hold through time, Japanese cards often offer compelling value upside
Bloodbraid Challenger is close enough to Bloodbraid Elf to not stain the name, and at a mana value one greater, with the ability to escape, the Challenger hits differently and I'm OK with that
Weakness: Fire (x2) Resistance: Grass (-30) Retreat: 3 Durant - Metal - HP110 Basic Pokemon [C] Bite Together: 20+ damage