I don`t think you are that bad. Nor do I think tanks for example are less micro-intensive...
I would say if you really want to get better, play small teams, 1v1 or alone against bots (on a challenging difficulty ofc.)
What got me a lot of mileage was being forced to do everything on my own in solo-mode.
Otherwise maybe try to narrow down your factory-selection and try to get those really under control. In clusterfucks, micro is king, macro does not help you much because you lack the income.