In fact the printing of Unholy Heat (and to an extent Solitude) has mostly pushed out cards like Tarmogoyf out of the format, as the removal in the format is now so efficient that creatures either need to be one-mana, so you trade at an even level (Dragons Rage Channeler and Ragavan, Nimble Pilferer), too large to be killed by Unholy Heat (Deaths Shadow and Murktide Regent) or generate immediate value upon being played (Solitude, Fury and Omnath, Locus of Creation)
A Pokemon-ex from the Ruby & Sapphire era might seem astoundingly weak relative to the best cards from today, but back then, they were breadwinners
What are their colors
Defensive phase-outs like Teferis Protection also allow creatures to dodge boardwipes, edicts and other non-targeted removal, where many flicker effects simply return them to the battlefield in time to perish by the next spell you had been responding to on the stack
So, by carefully picking the Pokmon selected for the breeding process, you can greatly increase the odds of watching a Shiny Pokmon hatch from that egg