If Kroll was never much of a modernist, his work is clearly not in the traditional vein either. Generally speaking, he tended to simplify his subjects to the point where viewers would see that this was a stylistic intent. To this degree he was a modernist. I discuss in detail the problems artists of his generation faced in my e-book "Art Adrift."
Kroll's style varied somewhat over his career, so it can be a little hard to spot his work aside from paintings of nudes in urban settings (see the photo at the bottom).