Bold one: I don't know. Length and popularity don't always equal quality. Take the episodes of the Rugrats cartoon after it's first attempt at ending or the Twilight books.
Mind you I don't think it's the worst possible series.
Bold two: I think it would be over-simplifying to say that the series' length is the issue and but rather the issue is that the plot and structure that we got was meant for a shorter frame, especially since we're suppose to accept that continuity wise that not even a full year has passed. Even if you trimmed the non essential material, there would still be a feel that more time than half a year passed.
To look at some counterpoints:
1. Simpsons and even Rugrats works because there was never even a semblance of a series plot. You might have the occasional reoccurring arc, but other than that it's forgivable, especially as something like Simpsons is mostly suppose to make us laugh, whereas DC takes itself more serious in comparison.
2. Even with some quality issues found (like the anime's means off padding the arcs from Vegeta to Kid Buu), it allows more of a time passage. Plus other than possibly Goku's desire to be the strongest in existence there's no singular goal for the series.
Some would say that's a low point because there's not as much focus, but on the flipside, unless a writer has both the clout (presuming that part of the reason for keeping the series going is because of higher ups demanding so) and integrity to finish the story in a reasonable frame, then it can arguably work against the story.
Shows like Dragonball or something like Young Justice on the other hand can conceivably have it both ways. You can wrap up subplots and even have changes in the status quo without compromising the ability to do more stories.
Take Haibara for example. There's been signs that she has info on both the Apotoxin and The Organization. And to be fair to have her share that info with the cast would actually or potentially begin the ending of the series, so I can on the one hand appreciate keeping this piece of status quo in effect. Though considering how long the series continued past her introduction and all major arc events since then, I feel the moment the manga starts to wrap up and we have Haibara sharing more info will feel anti-climatic, inorganic and sudden.
Not to mention that there are things that could be allowed some change without negative consequences. Take the whole bit between Ran and Conan. 2 decades and she Gosho still won't allow her to be brought into the secret. And I ask why? Because ironically enough at least as I see it, it's basically something the would give readers the best of both worlds.
It's a significant enough change to shake things up noticeably and yet not so big as to require ending the series. Heck, since Gosho is trying his best to pad the manga out, the change would open up quite a bit a padding fodder. Even if Ran was brought into the fold just before the Bourbon arc, I'd argue that it would still benefit the series on the creative side. Additionally it allows Ran to have more substance as a character and provides much needed growth for Conan.
In short it's a move that good on multiple fronts, and lacks real downside. If there is a downside I'd like to hear it as to be fair there might be factors I haven't considered.