Most DR I have seen was designed well. That was never the problem.
The problem is what happens after. Production does not hold still — new workloads, changed configs, a database that moved, a firewall rule that did not get mirrored. DR has to keep pace with all of it, or it quietly falls behind.
And who keeps it in pace? Usually the same team running production. The same people firefighting live issues all day, for whom DR is the task that can always wait until next week. So it waits. Attention goes where the fire is, and the fire is never in DR. Until it is.
Eight months on, you fail over and discover your DR is a faithful copy of an environment you stopped running back in the spring.
The design was sound. The operations starved it. Day 2 is where DR lives or dies, and Day 2 needs someone whose actual job it is, not a production team doing it in the gaps.