I am very new to firsthand experiencing DS2 haters and people being incredibly toxic and illogical about some of the game mechanics. While subjectively, I think the ADP/Agility stat added both interest and depth that wasn't not in DS1 and was lost in DS3, I also think it is difficult to dispute that it helped balance out build styles. This, for me, increases the game's replayability and general playability. When people are whining about the stat they tend to neglect to acknowledge that ATN also increases agility at a reduced rate. The ATN stat that not only increases slots now, but also cast speed and number of casts. Attunement was also cleverly emphasized to be a stat to lean into as a pure pyromancer, as pyromancies have low total casts, slow cast speeds, and no innate cast speed on pyro catalysts, even moreso than other casters. Attunement also literally means tapping into people's energy which is a neat correlation as well.
Why is this relevant? Someone said in a rather ignorant comment below that agility and ADP forces people to build tanky or level adp. But that is a false dichotomy. And it is one experienced players can see through so clearly that I think they struggle to say a logical and respectful disproval of it. You can level attunement and achieve good agility and access 3 different styles of caster. Imagine a character that ignores ADP entirely and level vig/end/vit/strength. That character would have crap magic defense and poor rolling. But DS2 levels are very cheap and there being more stats makes levels less impactful (see how it balances out...see how a higher level meta is irrelevant...). So that character I just mentioned can invest into ADP to up their resistances, and levelling up int and faith just a bit will give you all the innate elemental defense you need. That character could go 40 vig/end/vit 50 str and still have approximately 45 levels to go before 150--a commonly cited soul level, which as mentioned before, does not directly correspond to the SL metas of DS or DS3 because 1) there are a different number of stats in each game, 2) levels cost significantly more in DS3 than DS1 or DS3, and 3) Absorption works differently in each game, and PERSONALLY I think Int/Faith rewarded players who didn't intend to spellcast much with good defenses for levelling them up AND strong pyromancies (and even stronger BKHs which was unnecessary but I am here for it). 45 levels that can be invested into magic defenses and enough attunement for two slots. You can specialize a bit however you want, and accentuate your build.
For those reasons, battle mages and paladins feel the best in DS2, as do magic ninjas and templar assassin style buids...specifically because of the inclusion of ADP, agility, and the adjustments made to weight load, stamina, endurance, vitality, and attunement. And since we're fanboying to shut up the detractors can we just repeat, that so many of these changes were bitterly tossed out in DS3 as if Fromsoft saw the backlash and said oh pls Miyazaki put it back to your way (the way that isn't new or innovative anymore...now it's conservative--not judging anything else but souls). Resilience was a completely useless stat in DS1, remember? Somehow it is more comfortable for players to see a stat everyone can ignore, than one that can influence status effects, and evasiveness... Where is the role-playing and adventure with that attitude ffs?! I don't understand why RPG fans would get upset at giving it a purpose. IF NOT for any other reason than to whine that something (in this case, i-frames?) was taken away or "nerfed". I think people just got a grudge because they had to look up how ADP works online to figure out the i-frame stuff. Even though it clearly says makes you more evasive in game.