I disagree. I think there is a reality. You're right to bring up counter-examples, but I'd respond as follows:
1. Neither Manek nor Ingram were brought in specifically to be shooters. That was a pleasant surprise. Both were playable without it. It's the guys who we bring in specifically to shoot, and then who lose the ability to do so -- that's the frustrating part.
2. Volume matters. Withers was shooting just over 2 a game. That's not nothing, but it's not going to move the needle all that much. Plus, the year before he was horrible.
3. Ryan shot at basically his career average (.354 versus .352), which isn't dropping off a cliff but one might have hoped for some improvement, either from age/experience or just better shots.
4. Manek shot 40.3% compared to his career average of .382, so that's basically a wash. He didn't get worse, but he didn't improve a lot either.
And that's kind of the point. We've had many guys just fall off a cliff; our success stories are guys who were basically at career levels. Ingram is the one success.
5. So you're right that the perception is perhaps skewed, but I'd bet an empirical analysis would show a decline. Evans is starting to find his stroke a little bit maybe, and he could right the ship (but even his FT % is significantly down), so it could change by year's end. But Sevenson? Sigh. And I have no idea about Luka. Henri is way up compared to his career average; let's see if he can keep it up. But again, it's a bad trade if we're getting a good % on 2 attempts from him and a bad % on 5 attempts per game from Evans.