Get good with Bloodborne or Dark Souls.
That's an interesting point, I think it's all about managing expectations. What I mean is yes the games are unforgiving: mess up two three times in a row and you're done, there's no pause button or replenishing health bar, but on the other hand it's just getting in the Soulsborne zone. I actively avoided the series because I thought I'd get very frustrated if I tried...until I tried and DID get very frustrated as early as the Undead Settlement in DS1, but I've been on these games almost exclusively since January and loving it!
There're no real "hard" bosses, in the sense that play them enough and they will all go down eventually. I mean, even Ornstein and Smough - a fight which I knew way before I played any Souls game - I took them down on my second attempt without having watched a guide or anything, I simply dragged Ornstein around the room getting some damage in here and there and then until he was dead, and then simply avoided/punished Smough until he was down. Soul of Cinder was uninspired, in my opinion, Gwyn on the other hand was very atmospheric, and the melancholic music was spot on. Artorias was epic, Nameless King and Lorian were epic, Midir and Gael less so - they are endurance fights more than anything - but overall and caveat that I haven't played Bloodborne or Sekiro, I do not find the series HARD, just unforgiving.
Of course people make it artificially hard by playing with lv1 characters and broken hilts for weapons, but that's not how the game is meant to be played!