Keep in mind that Congress was on avg 61% democrat during his 8 years. Filibuster and veto proof for the most part some years. There wasn't much he could as far as signing legislation he opposed. He also conceded some liberal legislation to get other things done. I always like to use the phrase "he did what he could with what he had to work with".
He could veto it and require Congress to override his veto. If he wasn't in support of the legislation, then you've got to at least try it, right? Especially considering that it takes 2/3 of Congress to override a presidential veto.
But, in reality, his tax cuts (which at least partially resulted in federal tax receipts being as low as Carter's), budgets (which
arguably did more harm than good by increasing the debt), and many other decisions were championed by him; they weren't forced on him by a majority Congress. In fact, Reagan basically got the budgets he requested without much, if any, Congressional alteration.
Again, Reagan did a lot of good, including closing tax loopholes. I'm not saying he didn't. But in regard to my original point regarding blaming Carter, the makeup of Congress doesn't have any bearing on that, and even regard to political decisions that were made during his presidency, most of them were agreed to (if not championed by) Reagan.