Appropriations is always a prize appointment because everything that matters ends up in its clutches eventually.Appropriations is still a great reelection committee because Members can steer tangible goodies to their districts, but it isn't nearly as good a policy committee as it once was, both because lots of spending is outside of its jurisdiction. House Ways and Means and Senate Finance handle entitlement spending and tax-code based spending, and the budget process, in place since the mid-1970s, places severe restrictions on what appropriators can do.
That said, Drum is certainly right that Congress is "famously disjointed," but the whole point of setting up intelligence committees is to try to align the committee system with actual coherent issue areas. As far as Zegart's point about appropriators undermining cuts supported by the Intelligence Committees, I'm less convinced. Without an authorization/appropriations split, I suspect that the authorizing committees (including Intelligence) would wind up even more the servants of their relevant interest groups than they are now. I suspect the process works better by encouraging those who want to make good policy to go onto the authorizing committees; pork is an inherent problem for Congress, not a consequence of the committee system or the authorization/appropriation split.
I fully agree with Zegart, however, that expertise on committees is a good thing. I'd like to see, as she suggests, the House follow the Senate's example and remove term limits for service on Intelligence.