Konoha would initially be in shock. Naruto is a hero to many in the village, and his sudden departure with Itachi, who was once considered a traitor, would cause a lot of unrest. The villagers might start to question the leadership of the village, wondering why Naruto left and if there was something they could have done to prevent it.
Well, in some fanfictions, Naruto might outsmart Konoha by using his unique knowledge of the village's secrets that others don't know. For example, he could use his understanding of the old tunnels under Konoha to his advantage in a situation where he needs to escape or gain an upper hand in a conflict.
Ruby's speed and scythe - wielding skills could be very useful in Konoha. Her semblance of super speed would make her a formidable opponent in combat. She could quickly dodge ninja attacks and surprise her enemies. Her scythe could be seen as a unique and powerful weapon in the ninja world. Weiss's glyphs and ice magic would also be a great asset. She could use her ice to create barriers or freeze enemies in place, which is similar to some water - style jutsu. Her summoning of the Arma Gigas could be a new and powerful addition to the battles in Konoha.
One possible reason could be that Naruto feels betrayed by Konoha. Maybe he discovers some dark secrets about the village that make him lose faith in it. For example, if he finds out that the village elders were involved in unethical experiments or plots against his friends or family, he might not want to help.
They could bring new ideas. For example, if they come from a different place, their cultural ideas might influence Konoha's fashion or food. Their presence might also inspire the local kids to work harder in their ninja training, seeing two new and exciting role models.
It would be a huge blow to Konoha. Naruto is a hero in the village, and his departure would leave a big leadership void. The villagers would also lose a great source of inspiration. Hinata is from a respected clan, and her leaving would also have an impact on the clan's standing in the village. Morale among the ninjas might drop as they see two important figures leave.
Economically, there could be some impact as well. Naruto and Hinata are popular figures, and their presence in Konoha likely contributed to the local economy in some ways, such as through tourism (people coming to see the famous Naruto). Their departure might cause a dip in certain sectors that relied on their popularity, but it could also open up opportunities for new shinobi to rise and bring in new sources of income for the village.
Naruto might forgive Konoha because he realizes that holding a grudge won't solve anything. He has seen the destruction that hatred can cause, like during the Pain arc. So, he chooses to forgive in order to move forward and bring about positive change. Another reason could be his respect for the previous Hokages and their ideals for Konoha.
One possible reason could be fear. Naruto has the Nine - Tails within him, and some in Konoha might be too afraid of its power getting out of control. They may not fully trust Naruto to keep it in check.
The kids in Konoha like Naruto would probably be very excited. They love new and different things, and Harry with his magic would be really cool to them.