In fact i'd argue the game starts off with its best storyline, which is the Bloody Baron questline, and each subsequent storyline is worse than the previous one.
I don't think I can definitely say I agree with this but I also don't doubt it as Bloody Baron was one of the best questlines in the game. I just haven't played it in so long and I tend to forget things that aren't super noticeable.
I know I remembered really enjoying a few things about Witcher 3:
Never felt compelled/forced to do tons of the side objective spam and the ones I did usually had a character introduce me to a side quest that had a promising premise or hinting at one.
Hearts of Stone was a good story with decisions that made me reconsider what I was about to do/say.
Bloody Baron was much like Hearts of Stone
Blood and Wine was good as well and I enjoyed its story and choices I remember getting bored of it towards the end though, which is a problem I had with the main story as well
Letho was in the game
I think generally speaking my favorite thing about all three games is the difficulty in morality of choices and I don't mean who is ultimately wrong or right but what your choices mean and if the punishment/reward to those actors are fitting to their deeds. And that's something that might vary from player to player. Some people might dislike Letho even but he was one of my favorite characters in the trilogy. I loved that after all of Witcher 2 I got to meet him face to face and I got to hear his side of all the events that led up to that moment and then make a decision. Obviously, I was sympathetic to his plights.
But often, the best quests and decisions in those quests never left me fully satisfied with my choice which was oddly satisfying. How bad does a person need to be to be condemned for eternity? How about losing a loved one? How about just death? And it's a complex question when a single person who randomly steps in gets to influence that. It's not a court system, it's not a criminal book, it's a human(oid) trying to sympathize with another and I enjoyed. It wasn't perfectly done or always well done. Sometimes I felt like my choice in a Witcher game was an ill informed one and sometimes that felt fucking awful and sometimes it felt like that's just what can happen in life. I did dislike how the choice in the three witches quest in Witcher 3 played out, I know it's somewhat hinted at but it feels like a stretch I would have known the full consequences of that shit.
I agree the downsides of Witcher 3 are definitely the combat (though it was a watered down but smoother experience compared to 2) and that it's so. fucking. long. I felt like the bloat of shit to do was there but not hard to ignore either. I also disliked I got some legendary weapon from a boss/mini-boss and then like a level or two later I killed a generic enemy and checked the loot and his common/uncommon rarity sword was remarkably more capable at dealing damage. Levelled based loot really annoys me like that. Baldur's Gate 3 looks like it does this but ultimately it's just sidegrades of enchantments sometimes I found a new legendary/rare/whatever armor piece but found that my build wanted the uncommon enchantment I had hiding in my stash for 15 hours more. Nothing just strictly "leveled up" like a loot based game and I wish Witcher 3 never did that shit. Finding more powerful things is fine, finding them every 5 steps is annoying.