Let me explain in-depth;
> What should be taxed?
Profits of the company, like all other (local) companies do.
> Amazon, as an example, has servers in country X. Country X taxes the transaction or the income from the server company.
Amazon has servers in Germany, Germany is unable to tax the transaction or income from Amazon, because;
1. The user completes a transaction either on Amazon (buying a product) or in AWS (running an EC2 instance)
2. If the user is a business, there is no VAT. Because VAT is applied only to the end user. (To prevent compounding effect also). If it was the end-user, then end-user already pays for their VAT, usually around 18-20% in the case of an EC2 instance. But that has nothing to do with Amazon. User technically pays the VAT directly to the government depending on where he/she is located and where the server is.
3. Obviously Amazon does not sell the products or servers for free, they have a markup or profit margin, let's say 40% for a 100eur EC2 instance. So, 40eur lands into Amazon's bank account. While other 60eur goes to the operating expenses. (ie. Electricity, maintenance, employees' salaries, etc...)
4. In this case, Amazon should be taxed from that 40%, (ie. from the 40eur profit). Luxembourg corporate tax is about ~16-17%. Mind that US federal corporate tax is 21% itself. For the sake of simplicity, let's take 20% as the corporate tax. This would make 8eur going into the government's pocket. while 32eur stays as the profit with amazon.
5. All other companies provide the same service and has no magical entity outside pays that ~8eur to the government. Which in turn used to provide services to the citizens. (For example, Luxembourg has completely free public transportation that works 24/7, subsidized by the taxes)
6. However, Amazon having a magical entity, they declare all that 40eur profit belongs to the US entity due to the IP rights. They essentially say 100% of the things that are produced in Luxembourg, by employees in Luxembourg even owned by the US entity. Therefore, they do not pay any income tax as in fact there is no income on paper.
7. Instead, since they were able to save that 8eur, they can reduce the prices of the services up to that amount. But instead, Amazon usually reduces prices about half, reducing 4eur for customers and other 4eur going into Amazon's profit pocket.
8. It all seems nice so far, since users also benefit from reduced prices, right? Unfortunately, no. In the longer term, it hurts competition as other companies must pay taxes and losing the customers [to Amazon].
9. When there is no competition left, then Amazon can just start syphoning all the 8eur profit back to themselves. Even setting the prices as there is no longer any alternative to go.
10. Not only it hurts customers, it also hurts the random person on the street; as they receive services from government which were subsidized by the taxes. You may say that Amazon can or may invest even better products or services, but that's again not helping the layman unless he/she is an Amazon customer. And mind that a citizen does not need to be Amazon customer to get their electricity and water running.
> Amazon pays delivery drivers in country X to deliver goods, and the driver is taxed through various means (vehicle, fuel, payroll, etc).
Similar to the above, Amazon does not pay VAT or any other service taxes for any of the services they provide. But the driver does! It is even worse for the driver when he/she uses Amazon because on the net balance sheet, the driver pays income tax from his/her salary. Pays VAT for the services they receive. If he/she receives 1000eur salary at the end of the month, they can use at most about ~60% of their salary to receive goods and services. (~20% income tax + ~20% VAT). Hence, there is a corporate tax that balance these scenarios. But evading it causes more harm than good in the long run.
> What is Amazon doing in country X that should be taxed?
All the profits (earnings, surpluses) they receive should be taxed.