Men already have estrogen, the same forms that women have. Men have similar estrogen levels to that of pre-pubertal girls, and after 50, men have more estrogens than women do.
Phytoestrogens are weak estrogens that can dock with and occupy an estrogen receptor on a cell. Naturally circulating estrogens then cannot dock with that receptor and activate it in a more powerful way. Taking weak estrogens may prevent cancer, but they also may inhibit natural feminization.
I don’t recommend phytoestrogens because you don’t need them. Your own estrogens are more powerful. There are many natural compounds like spearmint and myo-inositol, that can boost estrogens and reduce androgens that are not phyto-estrogenic in any way.
Some phyto-estrogenic compounds, like genistein and black cohosh, may help with prostate cancer. So, some individuals may benefit from them.