In Praise of Nerfs

[King of Nowhere]

There's a difference between poor optimization (making bad build choices) and being an idiot (making poor decisions that make no sense). Your example falls into the latter category.

so judgmental.

it was merely a case of not knowing what his own skills did.
which, for a martial, is quite easy. you move close to the enemy, you roll a d20 plus a bonus, if your roll is high enough you roll 2d6 plus a bonus. you want to increase that bonus if you can. you don't even need to be actually able to calculate that bonus, you can just declare you attack and the friendly dm will help you along.
for a caster, making informed decisions requires a passable knowledge of most of your spell list. for a druid, it requires that, and knowledge of your critters, and your abilities. it took me years to be able to handle polymorphs.
A green player will just pick the abilities that sound cool or have impressive descriptor. turn into a big animal to kick asses? nice. throw lightning at my enemies? great!
they don't have the knowledge to understand how the first is only good if adequately prepared, and the second sucks. and unless they are dedicated, the infrequent playing schedule (stemming from busy real lives) is not enough to learn very well.

It doesn't help that your game was, admitted by you, houseruled so far outside the normal assumptions for the game that it caused problems of its own

huh?
I gaveg everyone - including npcs - higher wealth, and I used npcs as main enemies. Where's the houseruling in that?

but the result was
- everyone has higher armor class thanks to loot, but the barbarian can still hit. he'll deal less damage, he'll power attack for less, but he still can hit the first attack reliably and smack for significant hit points. and he can use the extra items to cover most martial weaknesses
- everyone has higher saving throws thanks to loot, but the wizard can still hurt people. save-or-die will work less often, damage spells will damage for less, combat takes a bit longer; still, those spells are effective. same for the cleric, and people taking less damage actually makes healing more effective
- druids, on the other hand, couldn't reliably hurt people anymore.
and i've seen many druids, in different tables, built and played by different people, and i've never seen one that was effective against an opponent with heavy defence.
it's just that at my table, that was the most commonly encountered type of opponent.