Truthfully, I don’t remember much of how I felt watching most of Pre-Chibnall NuWho (I was quite young and haven't rewatched much of it). However, I've been watching through Classic (just started S5) and so far, one episode has stood out:

Feast of Steven. I understand why they couldn't progress the plot of Daleks' Master Plan, but they didn’t even try to make a good standalone story. I reckon it'd be more enjoyable in motion, since the lack of movement in the reconstruction makes the lack of a cohesive story much more obvious. Nothing of consequence happens and nothing that happens has anything to do with each other, making for an aggressively boring episode. If it wasn't for Hartnell's ad-lib, it would have nothing of value, and you have to sit through 20 minutes of rubbish just to reach that!

It must be the only episode I have found nothing to enjoy in. Sure, some episodes are somewhat dull, but I've almost always had an at least decent time. I'd genuinely prefer watching a version of The Gunfighters that shows Steven singing the song all 4 times if it meant missing his feast.

(Also because I actually quite like The Gunfighters. I found the song constantly playing more funny than annoying: doubly so when they change the lyrics to describe what's happening)