the point of a class feature?... perhaps the ability to grow with higher stats or enchanted armor?... Also don't forget that there are multiple ways a druid can get 16 ac as early as level 1 without casting the spell they could cast at level 3. How far does class feature protectionism go & why does spellcasting not count as a class feature? Once you leave the spherical cow of no feats no magic items noncasters have better average & peak damage than casters, generally better hp than casters, almost always better ac than casters, & because of 5e design choices for spells like excessive concentration tags & unused by design spells even the value of utility stuff spells can supply is regularly little more than questionable to "sometimes maybe but probably not worth keeping prepped".If a level 2 spell slot makes a class feature obsolete, what is the point of class features?
You get more spell slots than other classes get class features.
16 dex and 16 wis is a large investment. 16 dex/con is a large investment. A 2nd level spell slot is not.
I'll admit barkskin is a bad spell; the concentration cost is high.
But making it last all day and stripping concentration isn't the way to fix it.
Again we are comparing a 2nd level spell equaling the ac so so many classes in the starting ink still wet from character creation state. 16 dex & dex builds were a big investment in 3.5 when they needed to take weapon finesse & such, in 5e it means you are doin a dex build for what is likely a largely dex based class. The point is that it's a way dex builds can trivially obtain 16ac too. 16 con or wis on a fighter wizard druid or paladin might be a big investment sure, but for a MAD class like barbarian or monk who have other features that use those abilities not so much & that monk/barbarian could also get it with an asi to have 14/18 or 12/20 in those two stats.