In what sense is "a real love affair" not feasible in 1984?
A love affair in a book about state torture of the individual? A romantic interlude in a society full of spies? No, in a dystopian novel, where the author only works in opposites, there is no love. There's not time for it, no need for it, and, artistically, no objective correlative for it. There's only Winston and his bleeding ulcer and Room 101 and rats. The only thing that comes close to love are memories that don't last.
Orwell's thesis of 1984 focuses on the individual being crushed by the state. Winston becomes an unperson. One has no time for a love affair in this wholly painful novel. To have one would be to subvert its themes. It would be a sell-out, a convenient emotional appeal to appeal to a kind of audience that wants romance for the sake of romance.
Even though Julia gives him a chance at love, Winston rejects her. He chooses to love O'Brien and individual rebellion and thoughtcrime over her and marriage and hapinness, however brief. In O'Brien's flat, Winston chooses pain over love.
A real love affair cannot happen in this society because it is pretty much forbidden by the Party. People are not supposed to fall in love because romantic love would make a person more attached to their lover than to the Party. That's not how it's supposed to be.
So, you're not supposed to be in love. And you have the screens and microphones all over the place. How are you going to have a love affair when the party can see and hear what you're doing?
Because the Party can watch you, you can't really do stuff they don't approve of -- stuff like falling in love.