The Oceania itself could not be reformed from the inside, it had to be dismantled, and ultimately isn’t by the end of the book, yes. Orwell never tries to show how to fix the problem, nor does he explain the mechanisms or forces that led to Oceania. Thus, 1984 is a depiction of what could be, in order to say “avoid this,” without recommending a course of action.
Leftist theory on the other hand does focus on mechanisms, existing material conditions, frames of analysis, and propositions to enact change and what change to enact.
1984 is a fine book to read for enjoyment, but not for changing society.