Coming up with an interesting idea for a series is all well and good but that doesn't matter if they don't know what to do with those ideas after the first chapter.
That's how you get series spending weeks drawing out the basic introduction that should be in ch 1 (U19), repeating ch 1 over and over (Red Sprite), or just plain falling apart when trying to expand on anything beyond the basic concept (Golem Hearts).
All of those artist got serialized in Jump for a reason, and it’s because they have potential. Sure, not of those series were great, but you can’t demy the the creators behind have talent, and their own unique style(in writing and in art).
Yes, they could put out one shot after one shot, and series after series and fail. And when that happens, maybe being a mangaka, and jump isn’t for them.
But most of these guys are young, and a lot of them are fresh in the industry. Just because say, the U19 Guy, has a bad 1st serialization doesn’t mean his next series can’t be good. I may not look forward to it, but I’m not opposed to him coming back, and I’d still always give any new series a fair shot.