This is a tough conversation to have because there are no objective standards of quality when it comes to difficulty. What's easy for you might be impossible for me, and vice versa.
Now, I agree that it's unrealistic to demand an "easy" or "hard" mode from a developer, when that feature is not among its list of priorities. At the same time, I think it's totally fair for a consumer to cry foul if a game is pointlessly easy or painfully difficult -- to the point where it robs a game of its purpose and sense of fun. We evaluate games how we wish them to be, not how the developer intended them to be.
This in particular I agree with, if a game is hard just for the sake of being hard, and no matter after X amount of hours, it can't be beaten, then I have an issue with the difficulty... thankfully I've not come across many games like this, and despite how many people will say the Souls games fall under this bracket, I seriously beg to differ.
I do feel that the difficulty of a game should be left up to the developer to decide, on the other hand, I also think they should take into consideration whether or not their game is TOO hard to beat, unless of course that's the goal they're going for. Again, I don't really have any examples of this off the top of my head, since the biggest example is usually Souls and, well, yeah, I've already said that I beg to differ, lol.
Let's look at a couple of my favourite games... Final Fantasy X (Surprise!), and Bloodborne. One is a Souls game. (Oh shush, not by name but clearly it is!... and the other is Bloodborne, plot twist! :o)
Both of these games can be completed without any kind of grinding/farming, although chances are you're going to die multiple times on each one. How do you make either of these games easier when they don't have difficulty options? Well you can spend time leveling up to make yourself stronger, farming for better items etc. and you can also learn the attacks of bosses to prepare yourself for your win. Basically to make the games easier you have to dedicate some extra time, which I really don't mind.
This, to me, is completely fair... of course these examples are inconsistent since everyone knows that Final Fantasy X is MUCH easier than Bloodborne, but if we're just going with Bloodborne as the example, people may think "But where's the enjoyment of dying to the same boss repeatedly?", well to me the enjoyment comes from the feeling I get after finally killing a boss, it's a nice feeling to be honest lol... also I now have the platinum trophy so I get ePeen and bragging rights, something you'll never take away from me! :P