I think the issue is that Opus has gotten relatively worse and worse as the game has gone on. Criminal gained Sec. Testing, Kate gained the Prepaid engine, everyone got Hotel, Kati, and Sym Visage, Anarchs got enough card draw to find a steady stream of burst to supplement Kati, and Noise got more ways to find Pawnshop quickly as well as Cache. Opus decks have been in the same place since C&C.
The advantage of Opus is that it doesn't take up many card slots, so most of the rest of your deck is pure business. Because it's both easily tutorable and unlimited-use, all you really need is Opus and your econ is done. The fact that Opus is a known quantity is actually a huge disadvantage; knowing how much money you can make as the runner is generally possible in any deck. Unless you're drawing to find econ cards, how much money you have available on your next few turns is pretty easy. Opus, on the other hand, signals to the Corp that you pretty much have to click Opus X number of times before you have Y dollars to spend, which allows you to dictate the tempo of the game as long as you have some way to pressure runs. Worst case scenario is that the runner has Stimhack or Sure Gamble, which is kind of a nonissue or a one for one a lot of the time if you're just pressuring runs with Assets.
By contrast, Kati plus burst econ is hard for the corp to judge and much more click-efficient, Sec Testing Desperado is cheaper to set up and often a tempo gaining play rather than a losing one, and Cache Pawnshop and PPVP snowball in efficiency as the game goes on to become way more powerful than Opus.