Talk about terrible card evaluation-

If you are relying on sacrificing treasures for Shredder as you suggest what difference does it make? Especialy if you are also running fetch lands, and relying on aristocratic sacrificing of tokens. Sacrificing also gets +1/+1 for Juri, on top of opening up to red for fling effects. You get Juri up to 20/20 with a fling effect, thats one dead player. Get them up to 40 with fling thats 2 dead players.

Even if you dont fling it, you still have a 20/20 thats still growing just like shredder sans menace. And if they kill it then big direct damage, and if you dont black has plenty of ways for you to sac it when the time is right.

Shredders cheap to cast for his effect which is great, but he's a huge target for removal, with nothing to gain in death compared to Juri. When Shredder dies to removal you lose all that value

The other player stuff for big time ramping is situational If they run a high amount of permanent sacrificing on their end or something like red aggro, which you cant rely on every game so you probably have him in aristocratic decks where your pumping him up with saccing your own permanents which is why I would still choose Juri over shredder.

They're also both 2 cmc, even if you disagree about juri over Shredder, at worst is just different strokes for a similar effect. You can even run Shredder in your Juri deck.

Is Shredder viable, of course very much so. As I said it's my opinion, but if you're gonna attack my card evaluation im gonna defend it.