I love gameplay. My favorite gameplay focused games are Mario Galaxy, Resident Evil 4, Metroid Prime and Bayonetta 2. I still can see great gameplay in The Witcher 3. Is not only about the sword combat. To me, traversing the world and discovering amazing locales is gameplay. Engaging into amazing stories by talking with people is gameplay. Preparing myself with potions and certain equipment before a fight is gameplay. I was playing Her Story the other day and I was taking notes in real life. That is gameplay to me as well, aka mechanics that are fun.
Gameplay is this "ambiguous" term people have created that might mean different things to different people. Based on my own definition, hell yes W3 has great gameplay.
Then we are quite similar cause I agree with all that and I too just played her story and took notes in real life.
It does come down to personal taste so there is no right answer. I think there is some general consensus in some areas. I think combat has certain tiers everyone agrees on with the hardcore action games like DMC, Bayonetta, ninja Gaiden being the best at combat and then there are tiers below that. But even with that its still taste, someone people don't like the difficulty or how fast paced those games are.
So obviously l am me and I have particular tastes but is still try to see this in a general point of view by comparing to thise general consensus. Witcher 3 combat I feel is probably not even mid tier. I give it praise for needing to prepare and always having to be engaged, you can't sleep walk through a fight cause enemies are dangerous. But once you know the strategy for that enemy there isn't much to it, just do the same thing over and over. Witcher 3 is so ridged in its design it rarely throws you into situations where you need to mix things up. You will pretty much always fight the same groups separately. So it's not just the combat mechanics, the simplistic enemy encounters hurt the combat as well.
You mention exploration, I love exploration. Zelda is my favorite series cause I get to explore an amazing world. And believe me I lost 150 hours just running around this stunning world but nearly every where I went I wanted more. I wanted the sense of discovery to match what I felt in other games, mainly Zelda. I want me the player to be the reason I found a mysterious cave. I want to be the one to solve a puzzle and find some brand new weapon. I want to see something unreachable and have to figure out what do I need to do to reach it. That's the part of exploration that engages me, and witcher had almost none of that. Everything has a waypoint, everything has a marker, and that damn red line telling you exactly where to go. Obviously the flip side would be to not guide you at all and then get lost in this huge ass world cause it is not designed like a Zelda game. So i understand why it's done but I don't think that makes for compelling exploration.
As for story it's where I understandably differ from many. I love a great story if it fits with compelling gameplay. TLOU, stunning achievement in storytelling with great gameplay. Still not one of my favorite games. To me story is just not that important, a good Zelda dungeon for instance will engage me in ways a compelling story will never do for me in a game. That's just me, obviously I know I am basically in the minority on that now.