Not sure I agree that season 4 was the best. I’m in the camp that felt the pacing was off. But then I really liked seasons 1 & 3, and ran hot and cold on season 2, which pretty much makes me an outlier among Discovery fans.
Discovery season 4 once they get outside the galaxy, is amazing, seeking out new life and new civilization, discovering a novel method of communication, and solving a galaxy spanning threat by talking.
As much as I like to see elements from the Relaunch novels brought to screen, in this case I pretty much knew where the chase was leading, based on the final Voyager Full Circle novel, and that took away some the wow factor of the contact with the 10C.