TOS also has some truly awful episodes, but it's pretty easy to ignore them.
I think the low points of DSC and PIC stick out for two reasons:
Recency bias. It's been 15 years since I last watched Code of Honor, and I rarely even think about it except when it's time to make memes about season 1.
Serialization. You can watch TNG, skip bad episodes like Code of Honor or Sub Rosa, and not really lose out on anything. But if you watch DSC and skip a bad episode, you blow a giant gaping hole in the over-arching story.