What is morally wrong about it precisely? Bloody hell, some posters have such narrow viewpoints! A stint abroad might widen your horizons a bit.
We are just ordinary Brits who happen to live elsewhere. It's actually quicker and cheaper to get to my sibling's house in the UK from the EU country I live in now, than it would be to get from many areas of Scotland to my sibling's house.
I am back in the UK minimum six times a year too.
Just because you live in a different country doesn't stop you being British or loving your country, or being invested in its politics. Many British expats have children who will eventually return to live in UK so are naturally invested in its future. I still eat fish finger sandwiches and listen to Radio 4 if that is your criteria. I also still pay some tax in UK too.
Not everyone has neat lives whereby you marry a person of the same nationality. Not everyone can pursue their career in the UK. I didn't particularly want to move abroad but I compromised because my husband isn't British. As it turned out, I love where I live now but it doesn't mean I am not interested in my own home country's future success and prosperity. I have also known people who left because they can only find the job or medical treatment they want abroad.
Citizens of other countries, such as Spain, are entitled to keep dual nationality and vote in the Spanish elections however long they stay abroad. That is a sign that the Spanish state recognizes that you don't change who you fundamentally are even after 25 years. Before the law had been changed and we were part of the EU, we were completely disenfranchised because we couldn't vote in our adopted country or back in the UK. I would argue that is more morally wrong tbh!