That said, I do agree that it's the Medium Armors with no DEX bonus restriction that are complete bullshit.
It sort of feels like their design was done with older DnD rules in mind... Y'know the ones where spell casting is restricted when wearing armour and resting required removing the armour (So if you were ambushed while resting somewhere not completely safe, you'd not be equipped)...
But since 5e ditched basically everything interesting about armour classes... You have medium armour being objectively better than light armour/robes without the DEX limit... (Lets not even get into the comparison to Barkskin... A level 2 spell that requires Concentration and doesn't even get ANY DEX modifier, let alone uncapped...)
It's so weird to have mages running around in Medium/Heavy armour because there's no drawbacks (Besides missing out on some robe bonuses, of which there are few that are particularly noteworthy)... I mean, it makes sense for like a Tank Wizard that's using Heavy Armour and Abjuration School to nullify damage. But it's strange to see your normal Fireball slinging Evokers and Sorcerers clad in armour...
To say nothing about the Medium Armour Mastery Feat which specifically boosts your max DEX bonus with Medium Armour from +2 to +3 which is completely irrelevant when you simply use some Medium Armours that don't have a limit anyway...