Everyone is different and it's way better to give people the tools to make necessary adjustments than to force them to sink hours into a game and then have to start over. I do not understand why this is considered problematic.
matter of taste. some consider this kind of design more inclusive (it is, especially for handicapped people), others like the casualness of it, then others think it's great when a game caters to them and their individual needs. for me it absolutely ruins the experience. paradoxically even when I'm not using it (the difficulty sliders), because psychologically I am always aware that any challenge is absolutely trivial. I can't turn that off. which is why I "hacked" the game in order to disable the sliders entirely.
I mean, there are any number of reasons to want to do that. Perhaps you built your character poorly and don't want to sink another 30+ hours into the game to 'do it right'
making mistakes is part of every learning experience. being punished for bad decisionmaking is, imo, essential to make any game feel challenging. if I built my character really poorly, why should I succeed? seems really counterintuitive to me, in that case why would any of my decisions matter at all?
also, if difficulty is set at the beginning of the game and you've never played.. why not just pick the lowest one? in that case having a suboptimal character build shouldn't be detrimental, no?
(a); you got blindsided by an attack vector you weren't really aware of and don't have on hand items to fix it .
totally fair point, thought this has imo nothing to do with difficulty sliders and everything to do with bad game design. me being the sadomasochist that I am, I gotta admit I would probably enjoy that. a game that doesn't throw me off completely every now and then barely keeps my attention. but I realize these are my personal preferences.
the combat system in the game is very finicky
this is clearly the case in skyrim, and I fundamentally disagree that the logical conclusion is to include difficulty sliders. if anything skyrim shows very clearly that diff sliders only exacerbate the problem. having finnicky combat is simply bad game design, stuff like that cannot be fixed by making all enemies hit like a wet noodle. it's not even a bandaid solution, it makes matters worse.
or the game isn't particularly well balanced and throws the hardest parts at you early on
that's just a bad difficulty curve, easily solved by making the player character very slightly stronger from the very beginning, but scale slightly worse into the late game. something I could solve with ~5 minutes in the ck.
basically, I believe there is almost always a more intuitive, more elegant, easier, more practical solution than readily available difficulty sliders. I don't think adjustable difficulty itself is a problem, adjusting it at the beginning or having the possibility for the player to cheat via console (or savescumming..) is enough imo.
Being able to switch the difficulty in-game lets me make it a bit harder when I become too powerful. *shrugs*
if you enjoy it that's great, no? all the power to you (literally).
And I beat my own personal best. 
