Thats one of the things I love about movies and TV, there is literally no way to know until the finished product is in front of you. All us armchair movie execs love to think that we could tell a great movie just from the script but I'm pretty sure thats not true. Many brilliant movies have had absolutely miserable productions -- Titanic famously went massively over budget, had tons of reshoots, had to have a second studio step in to help get it distributed, etc, etc and is considered a pretty great movie. Same with Godfather, Goodfellas, Platoon, Blade Runner, and a ton of other top 100 movies. Of course on the flip side movies like Suicide Squad, Alien Covenant, Flatliners, Justice League, etc had rewrites and reshoots and director problems and turned out to be terrible movies so who knows.
I'm excited for Solo, its either going to be awesome or a complete trainwreck, I don't see it just being "... meh" like TLJ with people like Ron Howard involved and the rumors that the script was the best star wars story script to date, that L&M got fired because they didn't stick to the script, that the lead actor is both awesome and the worst actor ever, on and on.