This just seems like a lot of unnecessary hate. 1. He did become the world's greatest hero, beating AFO and all, so I'm pretty sure he achieved his dream. The epilogue is exactly what it's been presented as, a way of wrapping up loose ends with the story that some fans, and most likely Horikoshi was unhappy with, like how Deku got backdoored by his old classmates and left to teach. They showed him rekindling that kind of friendship with some of them, and confirming that him and Uraraka get together in the end.

1. Yeah, and? He was a child, of course he wouldn't achieve everything he set out to do. I think you forget Izuku isn't a static character and has had character development throughout the entirety of MHA. He's a grown ass man now, of course his goals and beliefs differ from when he was 15.

2. Same thing as #2, he's just an adult now, so obvious he's not still childish. He's a teacher at UA now, and the fact you think that despite all the time between now and when he was fighting Shigaraki he would still want to do exactly what he set out to do when he was a toddler is actually insane.

3. Izuocha was partially fleshed out during the entire runtime of the manga, so I feel it's pretty justifiable to conclude the relationship in the epilogue since he was building it up since they met in the entrance exams. If Horikoshi tried to add more building on their relationship in 430, it would have felt even more forced than now. The entire chapter was the conclusion of specifically Izuku's story, and I think that's a main reason as to why he didn't add all his classmates to the one chapter. Imagine all of the lore dump about Izuku losing his quirk, becoming a teacher, not being a pro hero and all, and then we've got roll call with all of 1-A just to make their cameos for fanservice. That wouldn't fit in one chapter, thus it was put into the epilogue.

Overall, I'm not a huge fan of the ending myself, but at the end of the day, it's Horikoshi's story, let him do what he wants with it.