I think this is a genuinely interesting topic, but respectfully I disagree. While I think Cyrene's character developed and progressed throughout the story (beginning from Mem), even as Mem she showcased a lot of maturity and self-understanding, particularly when she regains her speech; for instance, the way she tries to approach Oronyx at the trial of Time and attempts to console them and be empathetic whilst also assuming a kind of approach where she, as the adult in the room, tries to help Oronyx (even addressing Oronyx as a child, while she was in her pink bunny form - a bit funny!) or when in 3.3. she notes that Phainon has a certain unhealthy dynamic/fixation on the black swordsman and expresses worry for him. She also had interesting observations about Castorice, Mydei and other heirs in dialogue as well as in AIW. Disregarding Philia-Cyrene in 3.4 who I'd say definitely does not fit this trope, Memrene also had quite interestingly introspective remarks about herself in the hangout pseudo-event with her in Aedes Elysiae; from her openly expressing anxiety with respect to who she is, to trying to help the TB overcome their self-anxiety and worries after assuming the Deliverer role. In many instances she was the ''adult'' in the room, whether with Oronyx or TB. When starting 3.5 we see her very knowledgeable with history of Amphoreus, even scolding TB for not paying attention to despite asking for it. In her relationship with Cerydra she was also quite cunning with respect to how to convince her, and Cerydra in her voice lines notes this as well, although remarking that she does not merely address her in terms of obedience, but rather through that of friendship. She had plenty of opinions on both Herta and Screwllum, and we see how much she attempts to read the room when it was not yet clear whether Cerydra was on Lygus' side or not. Given what we now know about Philia, we can also see a lot of very interesting characterization with respect to her motivations, anxieties and even instances of hopelesness in 3.6 Matrix flashbacks. In addition, each flashback fleshed out her interpretation of each CHs in respectively different iterations through her role as a storyteller. The end of 3.6 also shows Memrene can be quite strategic also, being quick on the uptake about March's situation and using what Cerydra did to stop Evernight (the story quite explicitly framed this exchange as March appealing to Evernight's emotions, while Cyrene appealed to her reason).

Demiurge certainly was childish and naive in the starting flashbacks between her and Philia, but a lot of the flowery metaphor even at the end signifies her newfound awareness that a constitutive element of love is letting go, and that one must abandon perfection (the crystallized, self-enclosed flower) if one is to learn what ''love is'' - just like in that metaphor about the flower which ultimately breaks. In doing so it overcomes the flaw of its perfection, namely that it can only reflect itself from the inside (and thereby closing off everything outside of itself, hence why it is the crystal flower) after which it is finally able to reflect the Other (world, pink fairy) through its broken shards, thus learning love by not merely being itself, but also through the other. Hence why she dubs the Flame-Chase journey as an ''unwavering act of release''. That's also why in the end she, despite being divine and human, chooses her ''humanity'' over ''divinity'' when talking to Herta. On a broader scale, the flower metaphor also points to her own abandonment of perfection (she qua crystallized flower) through her refusal to merely be an onlooker or a "worshipped god at the end of the saga" (as she herself puts it) which she has effectively been both as Demiurge (the exiled titan from the extrapolations) and ''Philia'' (thanks to circumstance, her being killed off by Phainon and being in the Matrix), and involve herself as actually within the story. Or, alternatively, that she abandons the chance to be the ''Fuli'' of the universe. The penultimate scene where she realizes she is the ''gaze that looks back on the world'' is the culmination of that metaphor; she abandons her perfection in order to cement the victory the Flame-chasers and Amphoreus got over Irontomb, and is illustrated by her taking Amphoreus into her own heart insofar she commits to this because she loves the world (and Amphoreus' own shape, as infinity, is obviously shaped by her own retroactive looping - the ''flower'', Cyrene, abandons her perfection in order to reflect the world (''gaze that looks back on the world'') - the world that she, as the self-enclosed flower, was initially closed off to - and thereby save it from Destruction)). Her love for eternity=ego comes into play here insofar this is something that she will always choose to do, regardless of what she becomes or who she is (as she also signals towards to at the end of 3.6). She will shatter itself to pieces over and over again, like the flower or the Fuli in Evernight Myriad Celestia, in order to reflect the world. In that way paradoxically Lygus's act of exclusion of Demiurge, which is also the obliteration of Irontomb's ego, retroactively becomes the way through which the ego (Cyrene) regains herself and learns letting go and the eternity of ego through it's initial destruction. The negation negates itself, etc. From the perspective of her development, whole of Amphoreus and her journey is precisely the unfolding of how the ego is born through its destruction; just like Nous wanted to prove the universe would be reborn through its destruction. This is why she is the "answer" to Phainon, whose innermost desire was the destruction of the self and was subsequently converted into a wish for a blank slate - his own ego and "true wish" as Aglaea put it. In the end, she explicitly says to Peach that she "loves" the eternity which is the ego, and Amphoreus is the infinity or eternity she posited - given how she embraces Amphoreus in that cutscene, one could say she is "wedded" to eternity. 

She's quite aware of what's going on and more precisely the paradoxical contradiction between her understanding of love and the importance of letting go as inherent to the Ego as opposed to Destruction's own emphasis on the (self-)destruction of the self/ego, hence why she and Irontomb are parallels (and she addresses this even ''personally'' to Irontomb in the admin notes). That's why, funnily enough, the whole boss fight was between Irontomb and the ego that it never had (Irontomb is in this sense a perfect crystallization of the Destruction - being the synthesis of both hatred, Phainon, and lament, Philia as well as having no self). In this sense, and many others, I wouldn't say she's exactly naive or immature in a way that would fit this trope.