Naruto being a Shounen doesn't really excuse that. The only reason something is Shounen or a different demographic, only depends on the Magazine the Manga is running in. Other than that, it doesn't really mean much. There are plenty of Seinen Manga that could be Shounen, Shounen that could be Shoujo, Shoujo that could be Josei. These labels only come because of the magazine it's running in. To a degree, these magazines obviously have things they want to show and don't want to show, but even these things are rather limited and Mangakas can do whatever they want, no matter the demographic.
It's just the fault of Kishimoto's writing, that the romance wasn't good. Of course, you can argue that Romance wasn't the focus of the manga, which is obviously true. But why include it then ? Bad romance is bad, no matter the focus, it doesn't excuse it.
And no, I never expected Naruto to be with Sakura. It was obvious it's not going to happen. But if Kishimoto was going to make Sakura and Sasuke happen, he needed to write it in a way, that is believable and not just toxic.
Even Naruto and Hinata made more sense, especially because of the movie dedicated to them made this a lot acceptable, although still not as properly developed as it could have been.
There are other Shounen Manga and Anime that also have Romance and handle it better, be it Cross Game, Rurouni Kenshin, Inuyasha, Eureka 7 and the list goes on.
People need to take in consideration the type of character Sasuke was and the fact that he not only wasn't present with Sakura and Naruto for the whole shippuden series and now he is barely home in Boruto too. Though I do agree that Sasusaku basicaly didn't have any development.
To me it was pretty obvious who would stay with who since the beggining of the mangá, even though Sasuke didn't seem to really care about Sakura (saving for some moments), Sakura love for Sasuke something that never really faded in the mangá. Of course Kishimoto could just have ended the mangá without Sasuke getting married with someone, but I guess he needed Sarada for Boruto and making one pairing that was planned since the beggining finally happen would please most fans.
About the other shounens, I didn't read Eureka 7 or Cross Game, but I did read Inuyasha and Rurouni Kenshin and I don't think it's really comparable, first because of Inuyasha and Kenshing type of characters and also for the fact that the authors had a lot of time to handle the romance better, because Inuyasha and Kagome/ Kenshing and Kaoru had more time together.