From the WaPo editorial board:
His tax plan, far from being a courageous departure from Republican orthodoxy, relies on many familiar Republican tricks to justify massive tax cuts in an age in which the government’s burdens are increasing, not shrinking — and with even less than usual honest arithmetic.
Mr. Trump would eliminate income taxes on married couples’ first $50,000 of income and consolidate the current seven tax brackets into four. He would cut the top income tax rate from 39.6 percent to 25 percent. Not even Jeb Bush proposed slashing the top rate that far. Mr. Trump would drop the corporate tax rate to 15 percent from 39.1 percent, again lower than where Mr. Bush would go. Like Mr. Bush, Mr. Trump would eliminate the estate tax, a move that would benefit only the wealthy, as the federal government taxes only high-value estates.
Mr. Trump claims his plan wouldn’t starve the treasury of any revenue. That seems impossible. He claims he would do more to phase out income tax deductions for the rich and super rich, but he doesn’t provide nearly enough specific details, and he exempts from reform the mortgage interest tax deduction — a $70-billion-per-year tax break that overwhelmingly benefits the wealthy. Similarly, he claims he would limit corporate deductions, but, with a couple of exceptions, he doesn’t say which ones or by how much.
This is the most real and aggressive tax cut plan I have ever seen proposed by a presidential candidate.
And the WaPo editorial board wouldn't be coming out against it so viciously, if it wasn't real and aggressive.
For those who advocate real tax cuts, this proposal by Trump is magnificent.