Those softwares like Ansys and others can be very accurate, like most professional engineering simulation softwares nowadays. Nothing replaces real testing, but what using simulation does is shorten development times and costs. On the other hand, I disagree that sloped armor is not longer useful. The same mass of armor but not slopped will always perform worse. Also, slopped armor allows for better use of composites and/or reactive armor. One could simply use 150tons+ of steel and make an imprenatable tank, but it wont be very mobile. Sloped armor is just another feature among many in the unavoidable compromise between mobility, firepower and protection.