Not all Elves are good, as proven by this card. At base, it's too expensive. It's a 1/2 for 4 with a fairly bad ability. What other 1/2s are better? Callous Oppressor, Academy Rector, or Bitterheart Witch are better 1/2s for 3, 4, and 5 mana respectively. It's not like the fact that it's a 1/2 for 4 that makes it bad, 1/2s can be worth 4+ mana if they have a good ability. But, this ability isn't very good. Yeah, forestwalk can be good sometimes, but it's just not worth it here. Surprisingly, there are only 6 cards in Magic that give a target creature forestwalk (not landwalk, forestwalk specifically) and they are all green. Now, if we're talking about an Elf deck, there are only 2 cards that work, this card and Weatherseed Elf, and Weatherseed Elf is better. Why? Weatherseed only costs 1, which means it comes out earlier. It taps rather instead of having a cost, meaning it can be used on the fly without worrying about saving mana. Now, this card can be repeatedly used unlike Weatherseed Elf, which is its only saving grace at this point, because this can only be used on Elves, meaning that it's use is limited outside of an Elf deck.
Pros: Can used multiple times, gives forestwalk to Elves
Cons: Only give forestwalk to Elves, expensive