IMHO it's a pity they did not stick with "Druids will not wear armour and shields made of metal" as per the PH page 65
Yeah, it would be better balanced with some armor restrictions. Druids currently have the same AC (absent bugs) as fighters and clerics. It is hard to envision choosing a cleric when a druid can do the same core things, but have more utility, better resource-free attacks, and a much larger health pool with no downsides.
Barkskin spell implies that druids are designed to have around 16 AC. As it is now, there is little reason to ever cast that spell.
The main weakness I have seen is the lack of good, basic ranged attacks since druids can’t normally use bows or crossbows and most of the animal forms only have melee. I find myself using the long strider spell to be able to close in faster in animal form. Picking Wood Elf solves this giving bow prof and both Dex and wisdom bonuses.
Next I want to try a Circle of the Land Teifling druid that only uses animal forms for utility. I’ll use the mage armor trick to boost AC to 24 and then flame blade and good berries to outlast everything, along with the searing smite racial power. Maybe start off with a blur spell from the desert land domain to have even higher defenses, because 24 AC is not good enough. Plus side of this build is that you can actually have normal conversations with NPCs.