Technically Mormanism blame people, not God for this, everything in the church is done unanimously, and they had to wait for the last leadership person who was overly racist to die before they could do this.

But also, the belief is that people recieve from God what they are capable of hearing and understanding, God didn't change his mind, people just didn't listen or even ask the right question in the past to get this information. Lastly, both Joseph Smith, and Brigham Young said as prophecy specifically that the church would admit African heritage people into the church and into the priesthood, Smith likely ment it would happen in his lifetime, but he was too busy 'secretly' marrying and having sex with 10 or 12 teenage girls, poor guy must have been exhausting, before someone caught him and he had to get a bunch of revelation on how he wasn't just banging teenage girls because he wanted to, but because you know. God said. Anyway he was busy with the sex and also a group of followers decided after this all came to light to dress up in black and shoot him. So. He never got around to it. Young on the other hand probably ment like ''when pigs fly'' kind of 'it'll happen'. He was pretty deeply racist, his time frame wasn't like SOON.

Here's my advice, don't bother with the theology, just push the whole thing off the table and don't care. Would have saved me a lot of time. When you engage with the actual theology it's just... so fucking time consuming.