I tend to think people underestimate the amount of govt investment that happens in our communities which will be neglected if left to private enterprise alone.
There needs to be a balance on taxation as too low can limit the ability of the govt to invest when needed.
Also your point assumes money will fairly transfer from private business to citizens when businesses have lower taxes? I don't think that is necessarily true.
I don't know much about the British tax system so can't say if the announced change is good or bad. The market however appears to be worried.