I'll start:
Demon slayer
Naruto Shippuden was by far the worst popularity to quality ratio I watched. Naruto is like a 6/10 at best, but that's still solid. Shippuden was so bad I hate watched Boruto (mind you, I haven't watched anime since 2021), and even that shitty reboot had more positive qualities than the most overrated delivery of media known to man. I did think Sasuke vs Itachi + Pain vs Jirahya was the best section of episodes in the series, but the downhill after that mini-arc was absolutely unmatched. It's a 1/10 show just unironically.