That was not a positive. Reagan was duped by the Dems. They knew they could always raise the rates when they had the power. Besides, giving out deductions to special interest groups is how politicians pay back favors. They never have any real intention of keeping tax rates low. It’s a giant con.
You confuse what Reagan did and what the Dims did later on. By your logic we shouldn't do anything at all to the tax code now because at some point in the future the Dims can undo it.