Because it would be like reducing MGSV to "You shoot people", when there's way more going on there. MGSV's strengths were it's ability to choose how you tackled things, planning your mission, loading up the relevant equipment for the type of mission etc. Same exact thing in this game. The difference is the end objective, instead of killing/fultoning people out, you travel between locations. How you go to that location and what method you choose is up to you, and there's tons of ways to do it. Which way you choose can effect a person's experience drastically.
All the things people praised MGSV for is here, all except for the focus on killing/fighting (which is in this game too).
Mmmm, I think that's not a good example. If I had to describe MGSV in a short sentence, I'd definitely say "you stealth into places you're not supposed to be", not "you shoot people". It's easy to argue against a strawman.
I get that you also need to plan how you get from A to B in DS, but it really doesn't change what the game is about in my eyes. Again, if you're having fun, that's great, and it's totally valid, but why the vitriol for people who aren't?