I think the nuclear taboo was always a myth. It's always been the case that there were 2 groups of countries (since nukes existed). 1 group had nukes, but could also generally get their way conventionally. Another group either didn't have nukes but couldn't defend themselves conventionally, or had nukes and just hid behind their nuclear shield. Like the DPRK using nukes to keep the US at bay.

So the fact no nukes every got used was mostly due to the fact that the big interventionist military powers didn't NEED their nukes to win. Unless they were facing a country that also has nukes. In which case MAD applies.

But now there's countries that are beating nuclear powers conventionally, while also not having nukes, and not even being backed by a nuclear power (like how the USSR was there to back the Vietnamese).

Then the extra factor is that nukes aren't all that useful in most cases. They're too big. Too destructive. Not precision weapons. But the wars being fought now are less and less about precision. And more about just destroying the enemy entirely.

So the way I look at it isn't as "breaking the nuclear taboo" since I generally don't think world leaders care about stuff like that. I look at it as the conditions that motivate or demotivate a nuclear strike happening are changing.