Yes, it is sad. It's melancolic as well as romantic. The whole movie has a sad theme all over it. The rationalization of Zeon's cruel deeds to Hatte and Side 2 by Gihren and Dozle Zabi are particulatly chilling.
By putting more wood to the characterization, especially Dozle and Char, help the audience to understand the action they took in the original "Mobile Suit Gundam" (0079) animation. It also makes me wonder if the dramatization here was overdone, to the extent that some may question if Dozle is competent enough to be a fleet commander. Then again, this seems to match the Dozle of 0079 quite well, and sometimes the line between rational and irrational is quite thin in realism-oriented series like Gundam.
How I wish characters from the side stories such as Shiro Amada and Cima Garahau would appear in the Side 2's attack, but this is a re-telling of One Year War by Yoshikazu Yasuhiko, who will stick to the original characters from 0079, so that won't happen.