When people say a company is unserious they almost always mean that they're not thinking about, and taking seriously, the work that their customers do. This seems like a classic example of that.
It's a dumb phrase and overused in contexts like this.
Something does not have to be useful, benign, consistent, worthwhile, or deserving to exist in order to be serious.
For example: Losing an arm and an eye to a fireworks accident, being grievously assaulted in an alley, or having Microsoft arbitrarily delete all your data, are all very serious things. So, I think it is fair to say Microsoft can still be called serious.
Just because an entity is able to do things with serious consequences, does not mean they are a serious entity.
For other examples, see school shooters in the US.