[variety]

To be fair, sometimes proficiency in some framework or CMS or vertical skill area does matter a lot more than you think it does. Remember now, the problem isn't that they get candidates who don't know $whatever_niche_topic, it's that they "don't know what they don't know", i.e. they have no inkling that the general "depth of terrain" in that area is much greater than what they were able to size up from their casual acquaintance with it... or that they think they can hit the ground running on a project that a serious heavy hitter with 5-10 years experience in that "niche" area been working on, when of course they can't.

That said, if your interviewers are doing their jobs properly, they should be able to filter for (or simply ask about) that level of skill awareness during the phone screen.

More likely, when you get told post-interview that "we need someone with more experience in X" it's usually a polite way of saying that they just weren't, you know, all the into you, and are trying to save face on both sides by pointing to something dry and objective, rather than things that actually matter. Like you know, the fact that you were underdressed (or overdressed), all those awkward silences you had with that second or third guy you interviewed with (remember, the one who announced his presence in the room by slouching in a chair and saying "I'm hungover"), or that you seemed to exhibit a slight latency in your recognizing some technical term that's common coin in the circles they run in (and so therefore, you just don't have enough chest hair), etc.

[variety]

all the into you => all that into you, of course