A more powerful format tends to have more effective means of drawing cards and churning through a deck, it will do these things more quickly, and it will also tend towards having cheaper cards overall, thus commanding more draw effects so as to keep the tap running
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Once the Sixth Edition rules changes removed that structure, Regenerate shifted into the "shield" version that players know, but probably don't particularly love, today
It can help you hit your land drop when you need it to, and then you can Proliferate in the later game and get some nice value
Even if gunslingers and outlaws might run rampant through Standard, in the long run we're unlikely to have any single set have an outsized impact on EDH