Just because Congress isn't passing much legislation doesn't mean members of Congress aren't writing many bills. But as Lee Drutman and Alexander Furnas show, only the barest sliver of the bills introduced in Congress pass one chamber — and only a fraction of those ever become law.
"Members of Congress had no shortage of ideas for bills they wanted to become law, especially on the subjects of health, national security, public lands, taxation, government operations and education," Drutman and Furnas write. Those subject areas "accounted for roughly half of all bill introductions." Interestingly, about 40 percent of the bill introduced into Congress had bipartisan (as measured by 10 percent or more of the legislation's co-sponsors coming from the other party).
As for the bills that do pass, House Republicans are considerably better than Senate Democrats at originating the (rare) pieces of legislation that become law:
Some of that is because appropriations bills typically originate in the House, of course. It'd be interesting to see the breakdown if those bills were removed.