Vantaggi
The problems that you're expected to solve are actually interesting and can tingle your brain and make you think.
If you know what you are doing there's a lot of free time that you can use to learn/grow/do other stuff
Svantaggi
Terrible management
Old, out-of-date documentation
No SOPs
No official channels of communication
0 management (for better or for worse - in this case it's for worse)
The whole structure depends on one or two people and if you are not there for a long time, there's little impact you can do on your own and you depend on the seniors. And if you don't balance this out in the exact way they have imagined you will get called out and most possibly fired.
Very very frequent layovers, 0 stability
No career path