Infinity Wars was everything it needed to be as a big loud party movie celbrating 10 years of fandom build up, doubling on the humour, the action, the emotions and the characters and doing everything Avengers did in 2012 but bigger.
As a standalone movie is pretty lackluster with little "substance" and lots of spectacle and funny characters but, looking the movie with these lens is missing the point of what Infinity War is and what it wants to say. Just like Avengers, this movie is a celebration of everything that Marvel has built on this franchise, the characters, its quirks and gimmicks, action, its cliches and tropes, emotional investment and more, this amalgamation of movie's substance IS its big and loud spectacle of crossover stravaganza.
That doesn't mean its inmature, here Marvel shows that they have heard its most common criticisms and you can see that they have been excercising on improving (most of) its shortcomings, and by doing so they delivered a thrilling opponent, surprsing developments (for their standards), many many emotions and an incredibly polished popcorn blockbuster like nobody's bussiness.
This is AVENGER: INFINITY WAR