With access to 4 colors, there are an absolute ton of ways to get multiple lands onto the battlefield each turn, sometimes even at instant speed, meaning something as innocent as a Harrow can suddenly turn into 4 life and a combat trick or two
Lets look at the three most popular
Although Marvel doesn't inherently do anything when it enters play without some setup, at four mana, players could take their time over the first few turns accumulating Energy counters with Attune with Aether, Woodweaver's Puzzleknot, and Aether Hub, so Marvel could eventually be activated on the same turn it's played for a potential combo win
deck and sacrifice 4-cost Ichiji to play out 7-cost Ichiji, which is a 7000 power character with Rush on TURN TWO
This won't be the last we see of the Alolan form, as both Alolan and Kantonian Exeggutor feature heavily among the most valuable Exeggutor cards ever
Long term it depends