This is in effect what they did when they criticized an analysis of the proposal by the non-partisan Tax Policy Center. An NYT article on the analysis, which showed the plan would lead to massive tax breaks for the wealthy and a large increase in the deficit, referred to the Republican response:
"Republicans quickly dismissed the analysis, saying the tax cut framework needs detail before it can be accurately assessed. A nine-page proposal for a tax overhaul, announced by Mr. Trump and Republican leaders in Congress on Wednesday, did not include income levels for its three personal income brackets. It left the door open to a fourth level of taxation for high-income taxpayers, and it did not specify the size of an enhanced child tax credit.
"'This analysis is based on guesswork and biased assumptions designed to promote the authors’ point of view — rather actual detail from a bill that has not yet been written by the committees,' said Antonia Ferrier, a spokeswoman for Senator Mitch McConnell of Kentucky, the majority leader."
The claim that there is not yet enough information available to evaluate the plan is incredibly damning to the Republican leadership who crafted it. They spent months working on the plan. As their comment indicates, there are still important aspects of the plan that need to be filled in.
This should warrant a separate article telling readers what the Republicans were doing when they were supposed to be working on their tax plan. If the idea is that they will just decide major aspects of the tax plan in the last days before Congress votes (they plan to vote this fall) then it means they intend to put in place major changes in the U.S. tax code in a way that doesn't allow for serious public debate. This fact deserves attention.