There is no GDPR compliance requirement for personal, non-commercial, side-projects. You can gather PPI on all the people in the world and use it on your own for non-commercial purposes and GDPR has nothing to say about that.
In general, this is true, but only if the side-project is absolutely for own, private reasons. As soon as there any economic activity, the GDPR applies, which is a very low bar that even some personal side-projects cross.
I'm so glad that if I had a revenue generating side project, I wouldn't have to worry about that horrible twisted maze of burdensome nonsense as long as I blocked EU countries. It's nice living in the US and having some modicum of autonomy left as someone on the developer side of things.
As a private developer, I agree, yet as a consumer and professional developer, I'm glad things move in this direction. And I assume the GDPR will provide a model for US regulation (just as the DMCA has influenced the European market as well).
BTW: You don't have to block them completely, just don't target them specifically (e.g. accept their credit cards).
As a consumer and professional developer, I feel no desire to wield a power to unfairly bully web services with unreasonable demands about their data pertaining to me.