Difficulty and fun are orthogonal, one doesn’t exclude the other. Look at something like Celeste, it gets brutally difficult in farewell but never feels unfair.
A difficult game should motivate the player to get better, and that can happen while still remaining a fun experience. Nine Sols has a difficult combat system, but the combat feels fluid and fast-paced. Learning how to parry an enemy’s attacks and get in counter hits feels amazing, also you get lots of meaningful upgrades and rewards from everywhere.
Meanwhile in silksong you have a character with insane horizontal movement, then you repeatedly get pushed through narrow vertical platforming sections with flying enemies above, spikes on the sides. Killing a bell guy by agonizingly hitting them 1 hit at a time before they dash away out of reach again is not a fun combat paradigm and doesn’t create the power fantasy Hollow Knight excelled at.
The boss fights and >!Mt.Fay!< are fantastic but exploring the map just feels frustrating, especially when 90% of zones don’t drop any rosaries.
A game developer can have massive blind spots about their game, feedback can elevate the artist’s vision if responded to critically.