I didn’t like it. I had an exchange about this with some folks here on one of the RO threads a while back. I think the actual premise is okay, but the film lines up poorly with ANH, the ‘reactor as deliberate sabotage’ thing doesn’t make sense to me, and the fan service is lame. I do understand why people dig it, but it’s not for me.
I think it lines up perfectly with the original.
Galen’s sabotage is extremely subtle. All reactors in the Star Wars universe are unstable. I took it that he just compromised the exhaust port design in a way that would explode the reactor from the outside. Something that would go unnoticed.
I’d also add that knowing Galen compromised the first Death Star makes the idea of them building a second more feasible. I’m sure if it had been completed, the exhaust port would not have been a detonation point.