Exactly. Do some of you guys really need Limbo? If you have the Rinnegan already, the paths are plenty.
Bocchi couldn't have said it better.
But really...their are more OP things then Rinnegan such as Mokuton, Shakuton, Bakuton, Jiton, Some but not all Custom KT/KG or any of those other Immortality techniques. (Living Corpse Reincarnation, Jashinism, Jiongu, ETC)
Since Limbo is actually derived from the Deva Path then you can actually just make it less powerful; as you said and make in a rather long-range Shinra Tensei.
Yeah, the KG and KT that you listed can be absorbed by Rinnegan techniques. Living Corpse Reincarnation, last time I checked, only brought back zombies that could not use their full strength. Even if they could use their full strength, they are not Edo Tensei on the level of being able to regenerate and limitless stamina and all.
On its own, Jiongu and Jashinism are not OP. Combine them together, and you got a different story, but on its own the Rinnegan is plenty powerful. The only legitimate comparison to a fully decked out Rinnegan (plus EMS) is perfect sage mode or a custom Hyugan setup.
And Limbo cannot be derived from the Deva Path unless the controlling of gravity is the shadow doing all the pulling and pushing (with the planet creation tech being an exception). Otherwise, it is clearly a "Creation of all things" type of technique that does not necessarily fall under the Six Paths. If it does, it would have to be the Outer Path due to its power over life and death (and presumably a thing or two inbetween).
They use "shadow", but honestly, it is the creation of a clone in a different dimension/world that can affect this current world, more like a ghost than anything else.