Chaos, Poor Engineer Standards and Shady business practices
Pros
It's really hard to come up with many pros. I will say that for the right engineer early in their career, there may be opportunity to touch a lot of different technology in a short amount of time and really have a big impact. Unfortunately, I think this opportunity is largely a result of the engineering bar being so low, that it could be relatively easy to stand out. That same engineer would probably be better served going somewhere with more engineering rigor.
Cons
The main con of working at Kaseya is that it's not motivated by making great products. The main goal is to make a boatload of money for the investors who bought up a bunch of small companies, smashed them together and who now want to exit ASAP. Other cons that are a direct result of that reality are: understaffed teams, ruthless budget cuts, mediocre benefits/pay.