Excuse 1: Its all about those pipelines baby. Once they have the tech created to make the pipelines to make the systems they will be pumping them out every week!Well given the very first system is not done yet, and nothing can be found on the roadmap until end of Q1 2020, maybe we can expect a 2nd fully handcrafted system by the end of 2022 ?
Excuse 2: This one is only going slow because they are adding the assets to make systems. Once this one is done the rest will come quicker because the assets will largely be done.
Excuse 3: Expanded scope! We voted for it! (actually, they never voted on full planets) Of course now they have full planets instead of parts of planets there won't be a 100 systems any time soon but there will be more content in those few systems on release than any other AAA game!
PS: All actual arguments i've heard.