If it’s not connected to the grid then there’s zero decentralization. Only solar. Logic loop incomplete.
Discussion
I’m trying to follow your argument and give you the benefit of the doubt that maybe I’m missing something but in what way is having distributed independent providers of power not decentralization? I’m here to learn, not to prove a point so open to the idea I’m wrong.
Independent solar systems to power a boat or an rv are single source power generators. Grids with multiple sources of power generation (solar being one). Form a web of decentralized power generators. In the large grid scale(which most of humanity needs to survive modern life) solar simply increases power cost and reduces reliability.