Its definitely not the fault of EASA/EU. However Brexit is also not the fault of the British pilots. British pilots that do possess both an EASA license and UKCAA license might actually have a good position in the future.
Setting up a new AOC cost a lot of time, money and effort. And as long as you are not planning to start flying within the UK you don’t need one. So these companies require an EASA license and the right to work in the UK. I don’t see how that is “discrimination” towards British pilots. There are also jobs for FAA licensed pilots with the right to live and work in the EU. Similar thing.