Archangels is a good item in general for anyone who scales, aka why someone like a Kassadin, Cassiopeia, Anivia, etc buy it! Those champions don't have a very good early/mid game and rely on powerfarming in order to get to a point where they can dish out TONS of damage, so items like Archangels or Rod of Ages work well on them. I still personally recommend the other items because if you get first blood/couple kills and then come back to lane with just a tear, you have no extra AP from all the gold you just got, which means you're technically still not ahead of the laner at that moment, vs if you come back to lane with, say, a lost chapter or parts to it, that puts you ahead and you can then keep snowballing from there. If you aren't ahead and you come back with a tear, you're putting yourself much further behind and the like 30+ extra AP you get from Archangels late game won't be worth losing and being weak all game, it just gives your opponents more opportunities to force fights and close games out quicker.

Also, if you compare your first two items of Archangels + Ludens vs Ludens + Rabadons, the damage difference is too huge (or if you have to get an early Morellos because they have a Raka, Vlad, Mundo, etc, you really can't since you need to get Ludens as your second item).

I do love love love Archangels and I wish it was more meta for Lux, but Lux is a champion where you're usually looking to get your Luden's ASAP so you can one shot the squishies, snowball, and turn fights by getting those picks, or just dishing out massive AOE damage in teamfights and locking down targets with your utility. Luden's also gives you the waveclear you need, that way you can rush to objectives or jungle fights a lot faster, or even just clear the wave and back fast so you won't come back to missed minions.

One more thing to mention, I also do think the specific game matters too. For example, LCS players (thinking about PoE specifically getting tear on Orianna) usually farm for the first 15-20 minutes with only looking at objectives or small ganks, you can kinda get away with tear (they don't get Ludens second item though, they use Archangels as their mana item and then keep on their build path), but soloque is usually a fiesta and having more damage early on to snowball and also get your team ahead and get those early dragons or barons means much more. I think it also depends on the laners and what bracket you're placed at. In platinum+, they know how to close out games fast and press advantages and small mistakes that enemies make, but lower elos it is much less common, so you can get away with a lot more. That's why I always say, if it's working for you and it's not something thats really viable on Lux, like infinity edge or rageblade (although AD/AS Lux is sooo fun in norms haha), go ahead and do it! Sometimes, for fun in norms, I'll go ROA into Protobelt just because it's FUN! This guide is just geared more towards what is meta on Lux or what items fit her best, especially in a competitive setting.

This is a lot of text so I hope I covered everything and let me know if I can help with anything else <3

Luxeøn