You might as well say the same about “The Clone Wars.” How else would we have known about the ultimate fate of Sifo-Dias, and why the clones did a complete 180 on their loyal Jedi generals so suddenly?
The Prequels relying on The Clone Wars for important plot details (and important character development) is also bad.
The Prequels are just as guilty of overreliance on supplementary material as the Sequels are.
If you really are that invested in Star Wars to begin with, then what’s stopping you from WANTING to learn more about it?
Edit: In hindsight, I worded my response here too harshly.