I don't know how anyone could watch that episode and see anything other than an absolutely heart wrenching tale of love and how beautiful and sad and even stupid it can be. You don't even have to be gay to identify with it, you just have to be human.
I agree, and that complexity is part of why I loved the episode so much. It feels bittersweet, because I get the sense that if not for the whole world ending, Frank could've easily spent his whole life in the closet. It was cute to see him navigating a relationship with the same sweetness of a teenager with their first love, but that also comes with there being a pretty significant emotional maturity gap between Bill and Frank.
That by itself isn't an issue (and because of varying degrees to which LGBTQ people feel safe to be out, varying levels of romantic or sexual experience is a fairly common theme I've seen within the community irl), but I also think there were some iffy vibes in the dynamic which went unchallenged, likely because neither of them wanted to disrupt a dynamic that they felt lucky to have.
It reminded me a lot of a lesbian friend of mine who stayed with her first girlfriend for way too long because they were the only two out lesbians in the tiny town. They were an awful fit for each other and they stayed together for years longer than they should've because they felt like there weren't any other options (and indeed, there wasn't really, not in that town).
So overall, Frank and Bill's story was a beautiful and sweet story of love blooming in improbable circumstances, but it also had nuance from the subtle darker undertone to the relationship. For me, it highlighted that ultimately this was a tragic love story, and the tragedy was only partly caused by the zombie apocalypse.
I find it to be a great 1 hour of television, but due to Frank's manipulative nature and the aforementioned romance con it felt like, I wouldn't classify it as a good love story.