Hot take: I figured Fullmetal Alchemist Brotherhood was overrated for 4 years, then a coworker in Tulsa made me watch past episode 12 | Anime Discussions - Talk Freely
I saw a video essay once that said the first cour is basically a prologue and the show really kicks in around the Lab 5 stuff, which tracks with your episode 12 thing. The pacing up front is kind of all over the place, so I get why people bounce off it early. Once it finds its groove though it's hard to stop watching.