No, not missing anything. Trendiness wars with actual benefit.

Nope, you are right on the money. It’s just new and different, and people don’t like new and different.

Not being able to spawn other processes is actually a huge security and performance benefit when you know you're deploying to a virtualized environment to begin with. (eg: cloud).

Most (all?) attackers dont care about apps. They want access to your server to do other things. That could be downloading a monero miner or doing something as simple as mysqldump. Either way that's another program which isn't possible in a single process world such as a unikernel.