What emerged on Friday, in the final product agreed to by Republican members of a House-Senate conference committee, was a bill that layers new tax complexities upon businesses large and small, and which delivers a larger share of benefits to corporations and the rich than to the middle class.

It sets all tax relief for individuals to expire in eight years, while making deep and permanent cuts to the corporate tax rate. It limits one key benefit for taxpayers in high-tax states, such as New York, but otherwise does little to back up Mr. Trump’s promise last month that “we’re also going to eliminate tax breaks and complex loopholes taken advantage by the wealthy.”

The final legislation, which appears on track to be approved by Congress next week, offers little redress to workers who have grown to believe that the country’s tax law thicket advantages those with power, political connections and lawyers on retainer. Its evolution undermines a central selling point for a bill that is already seen by most Americans as unlikely to benefit them, according to polls.

Budget experts had hoped for a tax overhaul that stoked additional economic growth by eliminating targeted tax breaks, which would allow for lower tax rates, a trade that economists generally believe increases efficiency in the economy.

“The whole purpose of tax reform is to eliminate tax breaks to simplify the tax code and reduce rates,” said Marc Goldwein, senior vice president for the Committee for a Responsible Federal Budget in Washington. “But from what I can see, they only repeal one significant tax break, and very few if any tiny ones.”