I absolutely agree with the second part. DS9 knew what they were doing with the grit they added. They still held to Federation values for the most part, and when they broke them, it was a big deal. And they also put in enough lightness to balance it out, like the episode in the final season where the whole crew basically takes the day off to do a heist in the holodeck.
But when Discovery and Picard took the grittiness further, it was just terrible, and you can definitely see some of the roots of that in DS9