Almost anything is unobtainium these days. If you try to find the exact rationale
for a given part, that's wasted time. In general, you can't.
To get an idea of the situation, go to your favorite distributor, and issue a generic search, such as "microcontrollers". Now filter the "in stock" parts exclusively. On average, you'll get about a 10% ratio. The 10% availability is about what you get for ICs in general these days. It hasn't evolved much in several months. The shortage is rather stable.

But it's not just semiconductors either. Connectors tend to be harder to get than usual.