Don’t confuse tax credits with tax deductions. The so-called Freedom Caucus hated Ryancare because it still contained tax credits – that is, amounts that offset the taxes owed by the individual, dollar for dollar. Worse, they were refundable tax credits… that is, if the credit were larger than the total tax owed before the credits, the difference would be refunded.
Tax deductions are amounts that reduce the income that is taxed. They do affect the tax owed, but only indirectly by reducing the taxable income. If you have little income, deductions have little value, because there is little income to reduce. Moreover, the first few thousand dollars of income are taxed at a very low rate. If you have taxable income of $30,000, your tax rate is on the order of 10-15%, so a deduction of 1$ reduces your taxes by 10-15¢. If you have taxable income before deductions of $500,000, however, your tax rate on the last dollar is around 39%. Every dollar you deduct is worth 39¢. Consequently, tax deductions are actively regressive… they are worth more for the rich than for the poor.
So: right-wingers hate (refundable) tax credits, because they are just as valuable (in $) and more valuable (as proportion of income) to poorer taxpayers. They love deductions, which help the rich more than the poor.