Why the Brewster Buffalo was not simply hopeless

Were Brewster Buffalos hopeless against Japanese fighters?

No; they struggled in unfavorable conditions and against the best opponents but could compete with comparable aircraft when properly supported.

The Buffalo was not target practice for every Japanese fighter. The land-based aircraft suffered badly when outnumbered, short of fuel, or facing top-generation opponents. Against fighters of a similar generation and under less punishing conditions, they could hold their own. In the Force Z counterfactual, carrier-based fighter direction and an organic fighter screen could also make the available land-based Buffalos more useful.