I'm perfectly fine with the the Rogue One crew dying. Here's why:
1) Unknown characters. Their names were all new. Literally, they could have picked out any name in the SW universe (canon or legends) and said, "this is how they made their bones." They didn't. For someone to do this and live would make them a high ranking person that they would have been mentioned somewhere before now. Literally, when I heard the character names and recognized none (but Saw), I hoped they'd all die. I would have been disappointed if any had lived.
2) It gives ANH more gravitas. With a sacrifice of lives (not just the space battle but also the ground team), those plans are worth much more. Sure we "knew" that that was the case, but we hadn't seen it before now. Seeing it makes a difference.
3) It sets up the other Star Wars Story Movies as being a different. With the numbered movies being about Clan Skywalker, you know all the main characters have plot armor unless it is really important. They're not going to be killed of GoT style unless it is a huge deal. No one says that has to be true of the SWS Movies. Here, they can do something really different, tell a complete story with characters you are invested in (more on that in a second) without feeling like we are in for a new set of endless sagas.
My only complaint really is that ... they failed to get us invested in the characters. The movie was a series of events that involved some characters. The characters themselves weren't fleshed out in any real way beyond the most obvious motivations for why they went to the final battle. There was no element of shared comradery to the cast. No one helped another learn to use their weapon better. No one cracked bad jokes while in hyperspace. The Jedi Temple couple didn't talk about the old days back at the temple (one could have explains why he lost his faith and the other explained how he kept his, nor how their take on the force is different than a jedi's, or how about why they stuck together). There was no "I call it luck." "In my experience there's no such thing as luck," scene nor a "you needn't worry about your reward. If money is all that you love then that's what you'll receive," scene. Things like this don't take that much time but they make a difference. Things like that are a lost art in today's movies. If you're going to kill a main character off, make us care about them first so their death is all the more meaningful.