I think a lot of this comes from a slow heavy hitting or tank playstyle vs fast attacking/rolling play style. The faster pace of the game works a lot better with a roll/dodge based play style and nearly everything is easy as a result of playing like this. Pontiff being a perfect example of this.
If you play with a slower/heavy hitting build, it becomes more difficult I guess. But even so there's plenty of windows to be able to attack. Previous Souls game the slower build worked insanely well, heavy blocking/heavy weapons both made a lot of fights pretty trivial. Now it seems to be leaning towards faster builds being better and make it a lot easier.
I've also noticed some players tend to just spam roll constantly and don't focus on actually timing their dodges or paying attention to abilities. That play style is generally punished as the attack windows are a lot smaller, and mindlessly rolling away from everything can get you caught into combos.
Maybe it's just people who haven't played Souls game in a while either and re-adjusting, vs people who've invested some time and used to the pace of the game. I personally found the whole game easy, but I became used to the rolling style/timing dodges in Bloodborne, and when I got around to finishing DS2 DLC not too long ago.
I thought there was only 3? Default ending "Light the first flame". Second with summoning the Fire Keeper after giving her the eyes. Third with doing the whole Yoel/Marriage quest-line. There's a 4th?
Unfortunately I missed the 3rd and need to do it again in NG+, but going back in for NG+ can just steamroll through everything now that I don't need to explore, should only take a few hours total quest-line aside.
Following the path after Crystal Sage leads to a single optional (edit: actually mandatory) boss in Deacons. Progressing through Farron Keep leads you to more bosses/mandatory progression. Both are fine, might be worth getting to Deacons first and then going through Farron Keep after.