i) Jude's use of apocryphal material in v9 & vv14-15 raises a familiar conundrum, which I've often discussed. I'll take a someone different tack in this post.
This post will be organized like those movies that begin with a cliff-hanger ending, then–through a series of flashbacks–show the audience how the action got to this point, before resolving it.
I'm going to work through a series of positions I reject. By process of elimination, I will arrive at my own position.
ii) A critic might contend that it's special pleading for Christians to canonize Jude, but refuse to canonize 1 Enoch and the Assumption of Moses. If Jude makes positive use of these sources, and we venerate Jude, then we ought to share his high view of these sources.
Conversely, if we think the sources are unreliable, then we should downgrade our view of Jude. If it was right to canonize Jude, then it would be right to canonize 1 Enoch and the Assumption of Moses. Conversely, if it would be wrong to canonize 1 Enoch and the Assumption of Moses, then it was wrong to canonize Jude.
iii) And the argument (such as it is) logically extends to 2 Peter. Inasmuch as Peter makes positive use of Jude, he is, for better or worse, implicated in the fortunes of Jude.
iv) Let's consider the first horn of the alleged dilemma. Even if (ex hypothesi) the church should have canonized Jude's sources, that's no longer a viable option at this late date.
a) There are no extant copies of the Assumption of Moses. And the Testament of Moses only exists in translation in one 6C Latin MS. Moreover, the relationship between the Assumption of Moses and the Testament of Moses is difficult to untangle, given the fragmentary state of the evidence.
b) We don't have 1 Enoch in the original. The full text of 1 Enoch exists in a Ethiopic translation of a Greek translation of an Aramaic original. There are some Greek fragments, as well as some Aramaic fragments.
How can the church trust the reliability of a translation of a translation? Moreover, the textual transmission of 1 Enoch is ferociously complex.
c) A related complication is how much of 1 Enoch we're supposed to canonize. 1 Enoch is a composite book. Even within that anthology, the Book of the Watchers is a composite work. 1 Enoch has a very complex editorial history.
Even if the church should have canonized 1 Enoch, that's a lost opportunity. It's too late to rectify that judgement call.
v) Let's consider the second horn of the alleged dilemma. Suppose the church was mistaken in canonizing Jude?
a) It won't do for Catholics to exclaim: "We told you so! This is why the Protestant canon is so unstable. That's what happens when you don't have a Magisterium."
But on the hypothetical I'm discussing (for the sake of argument), the church of Rome made the same mistake. So either Rome never had a divine teaching office or the man in charge was asleep at the switch.
b) In principle, Christianity could certainly survive the loss of Jude. In terms of historical theology, Jude is a marginal book. The same could be said for 2 Peter. Neither book supplies the backbone of historical Christian theology.
c) At the same time, that's too facile. The problem is not so much with the loss of Jude (or 2 Peter), but whether the entire canon would begin to unravel once we begin to tug at certain threads.
In principle, Christianity could still survive. It would have to contract into a core canon. The core canon would be defended on evidentialist grounds. The books which have the best claim to historicity. Testimonial evidence.
But if God allowed every Christian denomination to mistakenly canonize Jude, then that would introduce a serious degree of uncertainty into the Christian faith. It wouldn't be the end of the world, but it would be damaging.
Again, these are counterfactuals. I propose them to dispose of them.
vi) I think a key lies in the relationship between 2 Peter and Jude. Most scholars think Peter uses Jude. I won't rehearse the evidence.
Assuming that's correct, it's instructive to compare and contrast the parallel passages where Jude is clearly using apocryphal sources.
a) 2 Pet 2:11 paraphrases Jude 9, but eliminates the identifiable references to the Testament/Assumption of Moses by recasting the statement in more generic terms.
2 Pet 2:18 repeats the boastful motif in Jude 16, but eliminates the quote from 1 Enoch (in vv14-15) which forms the lead-in to the boastful motif.
A number of scholars think Jude 6 alludes to 1 Enoch, and 2 Pet 2:4 parallels and paraphrases Jude 6. If, however, Jude is alluding to 1 Enoch, that's far more oblique than the sources in v9 & vv14-15. So Peter doesn't need to omit that or recast it in generic terms, since the underlying source is already pretty obscure.
Mind you, I agree with Daryl Charles that this is not an allusion to 1 Enoch.
vii) To judge by how Peter edits Jude, Peter suppresses the references to apocryphal literature–by paraphrase or outright omission. How are we to interpret his redactional practice?
a) One possibility is that he's correcting Jude. However, I think that's implausible. If he though Jude was so lacking in critical discernment, why would he make such extensive and positive use of Jude in the first place?
b) Another possibility is that he thinks Jude's sourcing would be misleading for Peter's audience. Peter may have felt that if he simply quoted Jude, Peter's audience would draw a false inference regarding the authority of the apocryphal sources. So he protects his audience from treating 1 Enoch and the Assumption of Moses as inspired scripture.
Jude's letter may have been a very in-house affair. Jude may be manipulating this material for polemical purposes. His audience understood that. But in shifting to a different audience, the ad hominem context might be lost sight of.
viii) Assuming this explanation is correct, then Peter validates Jude without validating his sources. Peter intentionally distinguishes Jude, which he reaffirms, from his apocryphal sources, from which he distances himself.
In that case, it is not inconsistent for Christians to grant the canonicity of Jude even though they disassociate themselves from Jude's sources–except in the polemical vein that Jude may have exploited them. 2 Peter set the precedent.
ix) If so, that's analogous to how Matthew and Luke sometimes edit Mark. Assuming that Matthew and Luke are literarily dependent on Mark for some of their material, they sometimes redact Mark. There are various reasons. To polish the language. To say the same thing in fewer words. To adapt the material to their own audience.
But in some instances, it seems to be a case where they thought Mark's way of putting things might be misleading. To forestall confusion, they reword it. That doesn't mean the were critiquing Mark. But in using and reusing a source, they enjoy the license to edit the source. Every historian does that.