Going to put my spin on this with a personal opinion (Just want to make sure that no one takes this as an official response as I would like to contribute and discuss things with you all, also helps to get a better understanding and to refine points for feeding back to others

You can also look at it is a way to see it from another point of view, which then allows you to further explain your point. )
So from what I can gather, most seem to be in agreement with a game being challenging...that's fine but what about those that just want to experience the story or don't fancy being stuck in one area or on one objective for longer than one hour?
I mean I'm all for challenging game-play but I am also for giving players a choice. For example: I was playing some Ghost Recon Wildlands last night with a friend, we did a couple of story missions, where one basically allowed us to do what we wanted (We generally use the rule of, we try stealth approaches first and if the alarms go, we make our own decisions on how to continue, such as whether we run and hide to re-stealth or jump up and go full assault mode) after that we had a mission where we
MUST go undetected...failure is not an option.
So...as you can imagine, we failed it 3 times, first time was due to clumsiness, second time was due to not being fully aware of the guard's movements (One came from behind while I was in drone mode) and the third was due to missing a shot with the sniper rifle (Which turns out after switching to another sniper rifle, I was happier)
My point is, sometimes forced objectives aren't a bad thing. personally I do prefer where you can choose your additional challenges such as maybe for replay-ability you complete a mission as intended then you can go back and add "handicaps" to the challenge such as "Only use this weapon", "Go undetected"
I understand that some people aren't interested in game-play inspired by rogue-like games/hardcore mode (where you have one life, get as far as possible etc.) but I am also aware that some aren't interested in games that hold your hand either (believe me, I found this particularly painful considering I went from Elder Scrolls III: Morrowind to Elder Scrolls IV: Oblivion)
I guess in a way, I do like the best of both worlds...allowing a player to customise their experience by toggling/turning on and off settings, especially since personally I will play a game a number of ways (usually as intended firstly to get a feel of the game then hardcore after just to give that challenging aspect)
So for example and I know this will come back to bite me: Splinter Cell: Conviction...played the game to death, resurrected it and played it again all because of co-op and the game modes like Hunter and Infiltration. The game as intended provides the player with silenced weapons but also with loud weapons and sonar. My friend and I played the game for several hours learning the mechanics and once we felt confident enough or that we played through all the content, we switched it up by handing out our own handicaps....so, melee only, this quickly escalated to "shotguns only", which in turn created a new way for us to play, which was called "Rollie Rollie Shotgun"...where you simply roll towards your target and blast them with the shottie.
In short what I am trying to say is....games are coming to a point where they have to cater for many various play-styles but those play-styles also have to fit within the world and the world's reality. My "run and gun" friend for example doesn't necessarily like forced stealth missions and will avoid them the best he can but he's also not exactly a person that likes to do side missions
Difficulty in games is somewhat relative I find, I will always play a game first-time in Normal mode, mostly to experience the story with a slight challenge. Those that go straight from hard or insane...hats off to you but not for me until I know the game a little :P