I do want to be an ethical company, and I agree about all these decisions adding up over time. This article convinced me to deleted all of my MailTrack accounts and uninstall the extension.
I was using MailTrack for a while, and it's been a very valuable tool, but I can do without it.
I was also talking to some lawyers about GDPR, and they said that this kind of tracking is actually illegal for recipients in Europe, unless I explicitly ask for their permission to include a tracking pixel. So I was already planning to get rid of this, and I'm glad that my emails are now GDPR compliant (even for people in the US.)