U2 have never really been minimalists. That is- they are passionate and intense people. When they came to realise that they were being a little too intense they went for satire in the 90s. But frankly even when they did satire they put everything into that too. So it could be argued that they have always made decisions that would put some people off.
But as far as cool is concerned, it's not something that lasts for ever. Take the "27" club. All the 27 rockers were considered to be in their absolute prime when they died, and they forever stayed "cool". U2 were 27 when they put out Joshua Tree, which could be argued to be their prime. This can never be repeated.
So, yes they have lost their cool. But I don't care, nor should they. They are still the greatest rock band to have ever existed, and their longevity of career is testament to this.