[inglor_cz]

"Yet they have become less authoritarian"

Is this true for the UK proper? (Not the colonies, including Ireland.) Britain used to be quite a "lean state" domestically, while now being famous for having a lot of onerous laws micromanaging everything.

"now they can barely respond to domestic crises"

Interestingly, that was the case in the colonial era as well. Domestic problems in the UK were harder to address than wars on foreign continents. The Irish question was particularly stubborn. In 1914, shortly before the outbreak of WWI, there was actually a real risk of a civil war in Northern Ireland.