Okay.... so... first of all, I want to say, when I was a kid watching Cartoon Network, whether it was an anime from Japan, a DC comic book cartoon, or an American action cartoon, all of it was enjoyable to me. All the shows were a variety of different art styles even if traditionally the anime is always more violent and mature than the American action which are more kid friendly in comparison. I enjoyed programming on Toonami and Miguzi equally, however, it did suck that Toonami got taken to Saturdays only, which may have pissed off a lot of long time Toonami fans initially, especially if you were a fan of anime rather than American action.
Now to get to the main point. Miguzi is never going to be looked upon fondly like Toonami or even Jetix... Jetix started 2 months earlier than Miguzi and outlived Miguzi for 2 extra years just about, and this hurts for me to say because I enjoyed most of the programming Miguzi had to offer... while I loved almost all the programming Toonami had year after year. But let's look at the reality.... the selection of programming that Miguzi had was not exclusive outside of maybe Code Lyoko, which was the biggest red flag.
Let's look at Toonami in comparison... when talking about Toonami's existence on CN most of its years, there was a lot of exclusive anime on there you could not find anywhere else on cable, especially in a time before social media existed and when dial up internet access was still the majority of households... it was the only place you could see Dragon Ball Z, Gundam, Techni Muyo, Sailor Moon, Zoids, Yu Yu Hakusho, Rurouni Kenshin, Naruto, etc. you name it, and it changed the game.
Jetix, while not as impactful as Toonami, Jetix at least had exclusive content like W.I.T.C.H., Super Robot Monkey Team Hyperforce Go, Ying Yang Yo, Get Ed, the newest at the time Power Rangers seasons, etc. and you even had reruns of Fox Kids programming and Kids WB programming on there as well. The block was just more badass with fresh content on there.
Miguzi aired Teen Titans, Codename: Kids Next Door, Krypto the Superdog, Juniper Lee, etc. on there, shows that were already on other timeslots. Totally Spies had already been airing CN separately a whole year before Miguzi came out. Static Shock was from Kids WB. Pokemon and Yu-Gi-Oh, again, aired separately outside of Miguzi many times. TMNT (2003) and One Piece were already on FOX BOX/4Kids block. But you get the point. We can talk about Toonami being more mature compared to Miguzi being more kid friendly, but none of that is the reason why I believe Miguzi wasn't as successful. It's all about the exclusivity. Miguzi lacked exclusives... something that Toonami and even Jetix were strong at which made those blocks more memorable. So outside of Code Lyoko, there wasn't as much exciting or wow like to look forward to on Miguzi when the shows could already be seen outside the block or elsewhere.