I mean the core mechanism of interaction is the same as Rocket Arena, in that it's a shooter wherein you move your crosshair across the screen and fire to interact with the opposing players. So it's inherently closer to Rocket Arena, than it is to Smash, just on that principle of its interaction design alone.
I think your comparison obviously just paints the game very negatively. Because folks that really like Smash, often prefer items off because of various gameplay implications that items have. So describing it as Smash with items on, is not only reductionist, it misportrays the game as something that has those negative traits of Smash with items. Specifically, slow paced Smash brothers with items on would receive a lot of criticism because of the way that items work in Smash, they're randomly distributed.
So when you say it's 'slow paced Smash with items on' it conveys Rocket Arena as a RNG fest, wherein players don't have a meaningful influence over what happens in the game. But that's not Rocket Arena at all, Rocket Arena is a very skill-based, accuracy intensive shooter.
