I still consider gen 5 underrated. It sold poorly and let’s be honest people only talk about Hilda and Rosa from it because waifus.
Meanwhile Gen has great villains, a really cool sequel, a whole bunch of amazing features that made the game more refined, fun mini games like Pokestar Studios, a big cast of new Pokémon and old ones, actually story telling and characters, etc.
like it goes on and on.
Hell if you want further proof it’s underrated, Zoroark was set Up as the Lucario of the gen but never took off.
Poorly is a strong word for a game that sold over 15.5 million, a figure of which most franchises would kill for. Underperformed may be a better term as within its franchise it sold lower then the rest, but even then the gap between it and the next lowest (RS and SM) isn't so huge as to make it a 'flop' relative to them. It also should be kept in mind that it didn't have the benefits that some of the games above it did like XY and SM riding the Go boom, SM being an anniversary title, and having more time to sell within the system's lifespan.
Also, I'm not sure where you're getting the idea that the elements you listed aren't discussed at all. Visiting the Pokemon forums and even outside of them it's not uncommon to see praise for the Storytelling, the desire to see characters like N in Masters, some of the new features that people want to see built on better like Join Avenue, and the music which has been circulated around a lot as of late. The only aspect I'd argue gets overlooked is the Pokemon as aside from a spare few like the Cover Legendaries, Serperior, Chandelure and maybe Hydreigon, most have fallen to the wayside in terms of popularity and promotion.
As for Zoroark, it didn't take off due to reasons that weren't 'it's Gen 5'. It had a movie like Lucario, but unlike Lucario they made it an Event Pokemon making it harder to get, they didn't promote it at all in the main anime as it appeared in a filler episode towards the end, and a more limited media presence otherwise. It says a lot when Gladion's Zoroark was the best treatment the species has gotten, it was handled poorly by TCPi and the fact it held on to as much popularity as it did is amazing in itself.