It's one of the best fights this developer ever produced. I needed roughly 40 tries and had fun every time.
Thanks for the detailed response - I appreciate it. I'm sadly not sure we'll find common ground here, but I'll try to add a little clarity to my thoughts if I can.
Consider the Cleric Beast: it uses no particular attacks that differ mechanically from the enemies immediately before it: brick trolls, scourge beasts, that one executioner all use the same slow, wide heavy attacks and occasional pounces the Cleric Beast will use. Moreover, its key weakness to fire, beast blood pellets and serrated weapons are shared by the scourge beasts that directly precede it. If you're able to best the enemies on the bridge, that you'll need to pass to reach him, the Cleric Beast won't blindside you with anything you haven't already mastered.
By the time you reach Gascoigne you'll have passed through the sewers and bested the much faster stronger beastmen there. If you've explored, you'll have met Eileen the Crow and learnt something of hunters, levelled up and upgraded your weapons - you might even have even found the music box by talking to his daughter and picked up the Saw Hunter Badge to try new weapons if you're struggling.
All of these things, including new enemy encounters are consistent with the next tough fight you'll encounter. Gascoigne won't introduce poison or a rage mechanic out of nowhere, he'll used the same mixture of melee and ranged, albeit much faster and much harder - it'll take what know you and test it harder.
Now consider Sekiro's first tough encounter: not strictly a boss, but a sub boss, that occurs after just a few actual enemy encounters. He will immediately drop two new mechanics (trust and sweep) not foreshadowed previously that the game will only explain using on screen pop ups.
The next major encounter, the chained orgre, will introduce grabs and a red-eye mechanic on top of a moveset completely alien to anything yet encountered. Again, you won't learn by doing, you'll be told directly via an NPC/on-screen tutorial.
Next for many will be Juzuo, who'll introduce poison alongside a large mob and heavy damage, no tutorial at all.
Lady Butterfly will introduce illusions only in her second phase, again the tutorial will be a single NPC right before.
The horse boss is a completely new fight dynamic with an almost new grappling hook attack mechanic.
The bull introduces fire (I think), no tutorial, Genichiro lightning - like Lady Butterfly in his second phase, and like her tutorialised by a direct on-screen tutorial right before hand.
When you encounter BSB's crazy poison abilities in Bloodborne, it's not some wild new mechanic, merely a tougher version of what you've already encountered.
Not all encounters in BB adhere to this, I grant you, though as the game wears on, you'll rarely, if ever, find bosses tossing out some totally unseen mechanic - even Micolash's bizarre attacks are all pre-figured in small prior enemies.
In this way Bloodborne never needs to pause your game while it talks you through a new system, it shows organically through game design, rather than by telling. Sekiro seems to take a different tact and to me, it means that already tough encounters come with a side order of 'here, master this while you're at it'.
Genichiro as a test makes sense and I beat his first phase multiple times, but then - out of nowhere - I have a new mechanic to tackle and I can only practise that by resitting the test, even the part I passed, time and time again.
I found that frustrating, like being asked to complete a plate spinning course only to find the final exam included juggling too.
