The Nasuverse isn't as hard or difficult as people say it is, the actual issue is that as Type-Rey states, it's easy to misunderstand how concepts work in the Nasuverse.
For example, Shiva's 3rd Eye is a conceptual version of Shiva destroying the Universe... but it's framed in such a way that if he EVER used it on anything but the Universe, whatever he killed will be designated as a Universe(Imagine Sefar being like Kama is...). This is why Kama, combined with her connection to Mara already, could do the shit she does and have a virtual Universe within her... but why she also died to Parvarti's Trishula Shakti in the end, not because it has "Universal Power" but because Shiva killed her once so a simple recreation can do the same thing.
It's similar to how Heracles' God Hand makes him a legit nightmare to the point he's undefeatable in the right HGWs but if you so much as nick him with Hydra Poison(somehow), he will literally lose God Hand's protection instantly and all of his lives but the one since he ultimately "died to it"(He didn't but it was why he ultimately just killed himself).
It doesn't help that power can ultimately overcome conceptual defenses as well as shown a few times in FGO and even in the Anime and Manga when it comes to certain feats. So you end up with people who think the Nasuverse is more Conceptual Than Power... when it's closer to Dragonball Z in which Power > Conceptual in the right circumstances and other times, concepts can defeat other concepts which can lose to other concepts.
If you want the absolute best example of this, see Sefar vs. Excalibur at full blast, Sefar killed virtually all of the Divine Spirits and various gods and Machine Gods with her bullshit conceptual powers from the Umbral Star... and was killed due to Excalibur's simple but insane power.
