And what's the problem ?
The moon druid looks pretty powerfull from 1-4 and I read a lot of people saying that land is even more (not my feeling but anyway).
The problem is land druids get the same forms and also get additional spells. Moon druids can shape shift with a bonus action but that seems like a bad trade off.
Land druids should not have equivalent forms of moon druids. They are designed to be more spell casters.
Honnestly the bear is really better than any other form according to me for its 30 HP + its 21 strenght.
The other forms are good in several situations but I never used them in combats (except sometimes the badger to move, but it require 2 actions if you're a land druid)
The bird is not that much because you can't transform (bonus action) + jump (bonus action) in the same turn so it's incredible mobility is not really usefull in combats.