Our club split over whether to count the ending of a book we all hated

Something went sideways at our meetup on Tuesday and I still can't decide who was right. We read a 400 page novel that 6 of the 9 of us gave up on around page 150, and then the whole talk turned into a fight about whether a bad ending can wreck a book you already liked. Half the group says the ending is the last thing you feel, so it colors the whole memory, and the other half says if the first 300 pages were good that doesn't just vanish. I was on the second side until someone pointed out I couldn't even name a book I loved that had a weak finish. We ended up voting and it came out 5 to 4, which settled nothing. Where do you all land, does a bad ending ruin a book you were enjoying, or can you just pretend it stopped earlier?