I think the fact that it did take up so much time is explicitly why it detracts from it.

For the majority of the hour we totally lost the plot and were watching something else. Maybe if they actually inserted some apocalypse into that hour it would have detracted less, but if you photoshopped the fence out of the background maybe five minutes of the whole thing still would have had anything to do with the setting and events of the show at large.

As someone else in another thread had said, you could've swapped the setting to a cabin in the remote woods instead of the fungus apocalypse and literally nothing else would have had to been changed about the whole flashback. It's like the whole apocalypse never happened for the entire flashback, it barely impacted them at all, and the one time it directly did (the raiders) they used it as a fake out two seconds later and surprise! Bill is totally fine from that gut shot while Frank is now dying of a terminal illness and they lived happily ever after.

Like there's a compelling love story being told here, but it sure as shit didn't have a thing to do with "The Last Of Us." beyond cribbing the setting and vague ideas of a couple minor characters then doing literally nothing relevant with either.