We’ve never had carrier-branded phones. Not one. Only thing sold has been generic phones which accepts a generic SIM.
And that’s how the market is supposed to work. Free competition on devices. Free competition on service. Customers can combine as they like.
Granted you could buy carrier-locked phones rebated through a contract, but the carrier lock was time-limited and reversible and the phone was a generic, international model.
Carrier-branded phones was definitely not a EU-wide phenomenon.
If anything the introduction of the iPhone in Europe (launched using the very confusing US carrier-model) was what started pushing carriers into attempting to making new restrictions on how people were allowed to use their (formerly unrestricted) subscriptions.
So you got it pretty much 100% backwards.