The tax extension from the Aimeos company is only necessary if you want to do B2B or mixed B2B/B2C commerce (maybe also for EU/US wide B2C commerce where you have different tax rates per country/states).
Your criticism about multiple sites is very global and not helpful to improve things. What exactly do you want to do and what are the problems you've faced?
How to configure and adapt Aimeos based shops as developer
Forum rules: Always add your Aimeos and PHP version as well as your environment (Linux/Mac/Win)