I agree with the above points but I'll try to elaborate a little on this situation specifically.
A big reason tanks got hate was that they were that strong they could just facetank a crazy amount of damage while also putting out some strong, fairly target-agnostic damage themselves (due to the prevalence of % HP damage on many tanks' kits).
This led to a bit of a disconnect between what was expected, and what was delivered. If you see someone with a huge-ass HP bar and a lot of resistances, you don't expect them to do a hell of a lot of damage. They were able to live to put out multiple spell rotations on many occasions, though, and a combination of high base damages, and % HP damage led to them being safe and fairly effective. (Plenty of times I was surprised at the damage a good
Maokai could put out while also being pretty darn hard to kill.)
It was boring to watch 'the wet noodle fight' as a spectator, and things felt less impactful to everyone as a result. It felt like a slow grind, that got stale after seeing the same thing happen again and again. Two tanks fight each other. Twenty seconds later, they walk away on low HP. Welp. The only time things happened fast was when two squishies fought one another.
It didn't feel good. You didn't do too much to them as a bursty/sustained damage character. They felt like they did the same back to you, and it sucked to feel like that. You're damage-oriented, why is this tank doing proportionally similar damage to you?
(Although now I feel like we've swung a bit too far in the opposite direction but that's mainly sour grapes on my end. I'll admit I miss the days of 1v4 tanking. But I'm a horrible person who hates fun. And
. )