If you need an offshore corporation, it can be opened for a few hundred $, but if you need to do the same for example in Germany, then you have to pay 25000 EURO to found a GmbH.
Tax heavens have MUCH lower taxes, but they also have other benefits like very little bureaucracy, better privacy and better protection from lawsuits.
You will also have a lot of freedom managing your company. For example, if you try to move a German company to another country and that country has lower tax rate, then Germans will put additional punishing taxes on your company for the next 10 years, despite you are not living there anymore. You will never have that issue with offshore corporations.
No. Just because someone from north korea visited my website doesn't mean I have to comply with north korean laws. Otherwise you need to comply with laws from 200+ countries and need an army of lawyers+developers. Exactly the same with EU countries.
GDPR law is illegal. You cannot force a company to follow your laws if it doesn't have a subsidiary in that country (unless there is a special agreement between two countries). So I don't care if my SaaS is compliant with GDPR. Good luck trying to sue me outside of EU...
UI is not that bad, but the product is very complicated for startups. For example, I can create a website on Azure with just a few clicks as a single item in my account. On AWS, (even if I use Beanstalk) I have to create VPC, load balancer, security groups, S3 bucket for code and a lot of other things... not easy to manage and takes a lot of time!