enclave latitude tour

I drive a 2010 buick enclave with 39000 miles. I am retired so I do not drive much. When I went to the dealer a month ago the tech told me it was time for new tyres. Ilike these tyres except in snow the enclave fishtails. Also in snow when I tried to turn the truck went straight into a snow bank. Is this a problem with the truck or the tyres.