Chamberlain was wrong. That’s pretty well established, I think. Some modern apologists would blame his reputation on Churchill’s 1948 writings that savaged him as ineffective, but was Churchill wrong?
Best case, Chamberlain bought the UK time, while appearing as an appeaser and only very quietly funding rearmament.
Personally, I think one of Chamberlain’s greatest errors was staying “dovish” after Munich: had he adopted a more hawkish position upon his return, he might have kept his job and reputation.
As it was, his reputation being savaged after his death was as inevitable as the war itself.
It’s not as if there weren’t loud counter arguments being made, and not just by Churchill.