2 things: increased deficit spending in order to support tax cuts will have macro-economic consequences that can impact commerce in general (discussion of that is outside my competence, and could be lengthy)
also, the proposed curve of tax cuts seems to favor finance and in general corporate income. If that’s true, the Trump tax proposal simply reiterates trickle-down/supply side economic theory, which in my experience (Reagan, Bush, Bush) never worked on the real driver of the US economy: consumption (ie main street).
The wealth gap — much discussed over the last 10 yrs. with no narrowing of its width — would, based on past performance, only increase w/ these tax measures.
Of course, Trump and Mnuchin have little hope of reaching their initial proposal, but in this dealy admin we can assume that a 21% bus. tax is a very real possibility.