If, I recall correctly there are less than a million buy to let mortgages in UK. BTL landlords are in it for a longer period & do not have to sell if they dont need to. As such this tax can be avoided. There is always property flipping or turning it into a holiday let, failing this just wait prior to next election. You will see % rate being reduced or tapering relief being introduced.
Some forum users may know that even a high taxing Country like France they do not have capital gains tax after 20 years of ownership.