Since everyone seems against it, I'll go against the grain. It gives a lot of fans the opportunity to see their country in a home game at a major tournament. Peter Schmiechel mentioned on a podcast how this will be a really proud moment for Denmark.
Given the pandemic, I think there's a case it works better for fans. A lot of fans will get to see their home nation without having to travel. With all the travel restrictions, it puts a deterrent on fans travelling around Europe. If it's in one country, would government really be keen on flocks of people coming into the country from different places?
I haven't looked into but I'd also assume less money would be required to update infrastructure or build new stadiums.
That being said, I'm not a big fan of it but as a one off I have no real issue. The expansion which allows more 3rd place teams to qualify is a much bigger issue in my opinion.