It did what I would prefer more comic book movies do, which was establish a baddie without killing them off right away.
Sure, the conquerer "died" but it actually showed off how intimidating he was and how much of a threat all the other Kangs can be. Pretty much every other villain, except Loki, has just been eliminated, which is no fun imo, and Thanos was only teased until his movie, so while he was a major threat, the audience basically had to guess how bad he was gonna be.
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[This Sig was deleted at the demand of the Illuminati]