Uncharted 4 is a perfect example of great gameplay = / = great game.
It was by far the worst game in the series (and the least fun), despite the godly mechanics.
Biggest disappointment of the generation for me, I hated how the game metaphorically berated me for finding the previous games fun.
I agree with your overall point, but I'd take it in a direction that I personally find more interesting to discuss:
great mechanics = / = great gameplay.
There's a lot more to gameplay than just how your character controls. When you control Ezio in the loading screen of Assassin's Creed, that's not enough to judge Assassin's Creed's gameplay.
Most of Uncharted 4's problems are directly tied to the gameplay, even though gunplay and movement are top tier.
I feel like when people say, usually in a negative way, that a game has "great gameplay but bad everything else", they're actually putting a lot of gameplay stuff in "everything else", and only considering the core mechanics as gameplay.
When they say it in a positive way too, I didn't think MGS V was boring just because of the story, it's the gameplay I take issue with. Snake controls perfectly, but am I supposed to shrug off the boring mission design, terrible bosses, F2P upgrade stuff and all of that game's problems as "it's just the story, who cares"?
+
The endless climbing and boring characters hurt too. Elena was refreshing, but isn't really a major part of the game until she's a companion in chapter 17-20. Sully was barely there and seemed like a shell of himself. I guess he is older, but still. Nadine was the typical strong female type who basically just shows up to kick your ass twice. Rafe was better, but I didn't feel like the boss fight was necessary. Thematically great, but Rafe is a panzy and I couldn't care less about fighting him. Felt like they threw the boss fight in just because it's a game The biggest thing though is that Sam just wasn't an interesting companion and we spend the majority of the game with him. I wish that the Mafia actually got involved and Sam didn't lie, at least we would've got something more entertaining.
We'd get a really cool villain if they combined Nadine and Rafe into a single character. Or if Nadine had more interest in the search than she does, and her collaboration with Rafe was more passionate. The way it is, she literally only exists to punch people. It's Lightning V2, with all the punching Snow shit.
Elena was definitely the best part of the whole thing, but, as you said, severely underutilized.
I really really want to know how the original game was gonna be. Hopefully some of the actors end up talking about things they shouldn't in the near future.
About the Mafia stuff, it's funny that, before the game came out, I was really hoping they wouldn't make it a dumb cliche twist of Sam being a villain and whatnot, but the story was so boring and anti-fun in this game, that I wish we got a dumb cliche story that at least allowed for some fun to be had, and for Elena to be a major character throughout the entire game.
We spend most of the last Uncharted game ever with the worst character in the series. Thanks, ND.