There's nothing wrong with some romance in a comic book movie.... I just ask, like anything else, that it make sense for the characters and the writing is good - both things Bruce/Natasha failed at. Whedon surprised me there. But I'm going to go out on a limb and say they were Whedon's choice, not so much the studios.
I think going forward they will address it casually and quickly move on, as it wasn't well received. I expect the same from Steve/Sharon Carter, which was handled terribly in CW. Actually - I feel like they work as a great example of putting in a romance when there's no time or need for one.
I like Sharon Carter a lot and thought the Russos have done well to develop something with limited screen time. For me it makes sense 'coz I can assume Sharon formed opinions about Steve while she was watching him in TWS, and whatever she heard from Peggy. And in TWS she's already on his side - upset that the Captain is being hunted, joins his side pretty fast. (Still going through the comics and I hadn't known Sharon Carter is a pretty strong presence there with Cap). I could see at this point since she's pretty well trashed her career for Steve that she's hooked up with him someplace in IW, along with the other fugitives.
I know a lot of folks didn't care for Steve/Sharon but I liked Steve and Peggy and I liked Steve and Sharon.
But for me Nat and Bruce - watching Ultron the first time I felt like what the *&&^
? It's painful IMO watching two very good actors do a good job and it's Just.Not.Working. IMO not even believable and that whole Nat/Bruce farm conversation drags the film *fast forward*. But there's other stuff too like when BW says Hawkeye brings the whole team together (what?).
And IMO Pietro's completely unnecessary
perhaps-death - because Wanda could simply have gotten truly angry on her own and they could have had her have some line telling Ultron "only monsters save the world by killing" or something like that and THEN ripped his heart out. E.g., she's firmly chosen a side. Or had Vision come and they take out Ultron together, at the last.
And why did Hawkeye, a trained warrior, not at least TRY to move when Ultron was coming? He had to have known that a moving target is harder to hit than a stationary one, even if there was little chance of not being shot. He's fast enough in the Avengers to dive off a roof, but in Ultron he just stands there?
Just think Whedon bogged down in trying to show emotionalism tho IMO there IS a lot of good stuff in Ultron.
