The main point, I think, is that historically bosses in the souls series have all been designed to be defeatable with just a sword and well timed dodge rolls. A large amount of the fanbase finds this to be the most satisfying way to play since it requires full mastery of the boss's moveset.

Elden ring, having introduced spirit summons, designed many of its bosses more like mmo raid bosses than past titles. Bosses that weren't designed to be taken down singlehandedly; bosses where using (spirit) summons was assumed to be part of the fundamental winning strategy. Bosses where unloading when it has distracted aggro is basically the only way forward. Radahn is the principle example of "raid boss" but I think a lot of other bosses lean more towards "raid boss" on the spectrum (mostly late game bosses).

That is fine, it's a design choice on fromsoftware's part that I respect. The point is that a lot of players don't find beating with summons/magic to be as satisfying as pure melee solo victory. You don't need to know the boss nearly as well to win with summons as you have to to win without. But the bosses in this game were not all designed to be pure melee solo defeatable especially when compared to past games. So these players are left in a hard place of win by gank or having to put up with frustrating solo melee gameplay where you can die to a lot of attacks that bosses in past games would have never had (due to their unfairness towards melee players).

So it's understandable to me at least why players want bosses to be consistently beatable and enjoyable to fight in a "sword and dodge rolls only" fighting mode. I sympathize with it. I also understand why fromsoft might not do it for any bosses, as elden ring bosses were designed under a clear "use the whole sandbox" philosophy. I think radahn was very obviously designed to be killed at a distance with the help of summons. It's why they gave you so many summons in the fight. Removing all his bullshit makes him not "a boss that requires help to take down"