The movie was fine. It's failing because the market is saturated with too much Star Wars.
The Star Wars concept is actually fairly limited -- it's basically good VS evil in very simplistic terms. The story was told quite succinctly in the original trilogy and things were wrapped up quite nicely.
While the prequels were flawed (though I actually liked Revenge of the Sith), George Lucas was at least smart enough to just put out a new movie every three years.
I'm sad to see "Solo" fail as it is the most fan-friendly and least "SJW" of the new Star Wars movies. I think it is suffering mostly from the backlash against "The Last Jedi" (which I did like but it was the worst of the new movies) and that I don't think the casual fans really want to see a new SW movie every single year.
If I was in charge of Disney I'd take a long view strategy of Star Wars. I'd shelve all the projects that they're talking about (Rian Johnson's trilogy, a TV series?) and just focus on making Episode IX. I'd also bring back Mark Hamill. Yeah, I know that he "disappeared" at the end of TLJ, but that could mean anything.
After Episode IX, I would pause for about 5 years before putting out any new Star Wars movie or television show. And forget about a Boba Fett movie -- the character is super cool but I doubt he can carry an entire movie by himself. I think that having an Obi Wan movie starring Ewan McGregor come out in 2025 would make a big impression.
And "Solo: A Star Wars Story" is a really bad title. The word "story" implies that it's just a throwaway tale and lacks the epic punch that these movies are supposed to be. Why not call it HAN SOLO instead?