Has "Lucky Friends" been disabled/bugged?

In the time I've been playing, I have made several lucky friends. However, in the past few months, I have since made new Best Friends, and continued interacting (trading, battling, sending gifts, etc) in order to trigger and re-trigger Lucky Friends with all of them. However, it simply hasn't happened.

I have noticed a couple of odd things - mainly the animations. I cannot "skip" through the items I receive through gifts, and the "friendship level increase" animation doesn't happen either (it doesn't "pulse"). The level does still increase with other friends (I have only been able to notice this by observing over a long period of time).

So has "Lucky Friends" been disabled, or is it bugged on some way, or am i just very unlucky?

You are probably just leaning on the unlucky side. I too have experienced the oddities you mentioned around friendship interaction, but despite those issues I can say that lucky friends have not been disabled. In the last week, I have become lucky friends with two different trainers.

Based on my experience, going months without becoming lucky friends is not uncommon. I will occasionally go weeks to months without getting a lucky friend. I have several friends where it has been at least 6 months since the last time we were lucky

No.

Lucky Friends are a 1% chance of occurring per friend on each day you interact with them. You would typically expect to wait over 3 months after reaching Best Friends before going lucky with any individual trainer.

If you interact with a Best Friend every day for 458 days (or with 458 Best Friends once, somehow), you still have a slightly higher than 1% chance of not having gone Lucky a single time. Such is the realm of low percentage odds: it becomes a lot more plausible to have a really dry streak.

Without knowing the exact numbers in your case I can't definitively say whether or not you're "really unlucky", but my guess is that you're just experiencing a fairly standard level of "unluck" - it just seems a lot worse when you're dealing with something so rare to begin with.