Avast needs to pay closer attention to quality, and much less attention to how the UI looks.
In particular, bugs that cause significant system malfunctions (e.g., problems with system startup, BSODs, lockups, problems with specific applications) should be much rarer than they are.
I buy an antivirus to stop viruses while minimizing side-effects, not to look at a beautiful UI.
Please, Avast, improve the product's core quality.