Detective Conan, the story of a high schooler shrunken to the size and age of a six year old, takes over 900 chapters by now and supposedly spanning over multiple years and yet he hasn't aged a single day since!
As entertaining the idea was, this series is going on much too long. Conan is nowhere near closer to getting his real age back permanently than he was in Chapter 2 and we're getting close to 1.000 chapters up to now.
While I stopped watching the anime years ago, mostly due to the series no longer being shown on German TV or newer episodes taking too long to being released in the west, I do still read the manga. Unfortunately, this series is deader than any of the corpses you can find on every corner in this manga.
Perhaps this is Aoyama's lifework and he wants to end the series as his final manga before retiring. Or perhaps he's trying to get every creative murder idea out of his head to make room for new ideas, though looking at the cases as you proceed in reading, they all begin to be pretty much the same just with some name changes here and then.
The huge amount of characters doesn't make it any better. Some of them appear and then they disappear for so long that, when they are mentioned again, you can barely remember what was going on. And the constant pairings of Childhood Friends, whether Victorious or Unlucky, are just really boring since there is no dynamic anymore. These two have known each other since they've been kids. They're gonna end up together, you just know it. Moving on.
Some of the methods and ways of killing someone can still be entertaining to figure out, if you can figure out the hints that you generally lack in translated versions due to so many hints being wordplays on Japanese one may not know, but for the most part, Aoyama needs to stop this series. It lost all novelty and every new plot twist that actually has to do with the plot of "I want my age back and take down the Black Organization" just adds more layers that ultimately mean nothing.
At this point, my personal theory is that the series ends with Conan bringing down the Black Organization but getting fatally wounded and dying in Ran's arms as he reveals his true nature to her. I will continue to read the manga to see it through to the end, but honestly, my theory seems like a pretty good idea right now.