The problem is, the arc they gave Han in Solo means the rough, tough scoundrel we met in Star Wars who reluctantly fell in with the good guys, gave up smuggling, and eventually became heroic never existed. He was always a hero fighting for the for the downtrodden, always saw the good in people, and always gave up his fortune for the greater good. Talk about not being allowed to evolve.
Also, we've always had to live with the fact that his relationship with Leia was confrontational (the fact that the two weren't an item in TFA was a good way of dealing with that). But then you watch Solo and realize that Leia was the only woman he treated like that. It changes the romance arc in ESB from being the love that helped him lower his guard and let someone in to the story of Han really getting into his emotionally abusive relationship era.