-I think Cat raises the sensible answer. If you ask me, I would say it is not as beloved precisely because it does not offer everything you could ask for in a Gundam series. As a franchise, it started with the units not being that important. By which I mean, the Mobile Suit action was just a vehicle for the storytelling. The conflict, the tension, the human condition. There were stakes, there was something to fight for, or against, and there was reason to. And even if the opposing force was corrupted at the top, it was not black and white, and there were people, actual people, on both sides of the conflict feeling fear and hope and conviction. I think it doesn't resonate as much because it takes on a lot of common modern anime conventions, tropes if you will. It appeals to children, which is fine, a valid demographic to target, and it is a smart way to promote another huge facet of their business, Gunpla models. But it could be anything, a completely original intellectual property and be exactly the same. It is only Gundam and Gunpla because those are what Bandai owns and wants to profit from commercially. In-universe, for the plot and outside of obvious cameos and references like Ramba Ral being the direct inspiration for the older Gunpla enthusiast, there is almost a sanitization of the Gunpla hobby if I remember from watching the first GBF season. A disconnect from the models and the stories or characters attributed to them. They are almost a separate commodity. In Beginning G, and I am sorry if I tire people with referring to that OVA whenever the subject comes up, but they do acknowledge that the anime are a thing, and people watch them. I can't even tell you if there is a hint of the anime being a fixture in the Build Fighters world. I'm not sure if I'd want them to, as trying to say "They exist, this is just like our real world just with this gaming competition system.", and then adding the fantasy world and magic that animates the plastic in the models causes a little friction. A light competition taken seriously by the competitors is not a new model for a series, it's pretty common for sports-based series. But I think when you add this additional factor, of it not being just a competition, but a hobby and competitive sport based on an entirely separate entertainment property with decades of history and numerous entries, all containing their own stories, characters, and conflicts which the MS are present to allow those elements to be explored, rather than the MS themselves being raised on the pedestal like in GBF, people feel that in the Build titles, there is something missing.-