The escalating difficulty is definitely an issue. When your games are known for being hard, any backslide in difficulty is a disappointment to expectations (I disagree, but that's the idea, I'm convinced). And there's definitely something to be said for an epic series of battles, especially as a final boss. I don't see it too different than, say, multiple stages of a JRPG final boss fight (except, of course, way more punishing and frustrating).
That said, the spirit ashes in ER can make a huge difference in adjusting the difficulty of a fight. Depending on your build, Mimic Tear can completely trivialize fights. I just beat finished my second run the other day; I was having trouble with the final boss/es too, until I went to get and level up a particular spirit ash that made my next attempt almost disappointingly easy - and only at +9, not even +10! (What I mean by disappointingly easy is that it felt like a victory I didn't particularly earn. I did fine in the first fight, but in the second battle I missed almost every dodge, ate almost every hit from most big attacks. But since I had a decoy running around doing sick damage, drawing focus and dodging attacks like crazy, plus stacking a ton of defensive buffs, I was able to survive and heal through it all; I'm not even sure I did a majority of the damage in the fight. Not every boss fight victory where I summon help—ash or player—feels that way, if I feel like I still contributed and did well against the boss. But this time did feel unearned because I otherwise did so poorly throughout the latter fight.)
Anyway, if you're interested: Go to the altar of the moon, the south-Liurnia plateau you get access to at the end of Ranni's questline. I think her questline doesn't get shut out by progress at any point so you should still be able to backtrack for it if you haven't yet. In the plateau's NW corner is an evergaol with a bitch of a fight against a black knife assassin. Beat her and you get a spirit ash that absolutely shreds.
Back to the main point, this is what makes me a little torn on the difficulty in ER: it feels harder than ever before, but they also give you so many tools that can make those fights doable or downright easy beyond the usual option of "summon help" (which is still also an option). They even give you plenty of respec tears and upgrade items to, if you really feel like it, level up a new weapon and respec to use it. Like, I can totally give you a build to trivialize Malenia, or even just a particular helper summon. But I also see how that might be less satisfying than being able to overcome any given boss with a certain build through dedication and practice.
That said, the spirit ashes in ER can make a huge difference in adjusting the difficulty of a fight. Depending on your build, Mimic Tear can completely trivialize fights. I just beat finished my second run the other day; I was having trouble with the final boss/es too, until I went to get and level up a particular spirit ash that made my next attempt almost disappointingly easy - and only at +9, not even +10! (What I mean by disappointingly easy is that it felt like a victory I didn't particularly earn. I did fine in the first fight, but in the second battle I missed almost every dodge, ate almost every hit from most big attacks. But since I had a decoy running around doing sick damage, drawing focus and dodging attacks like crazy, plus stacking a ton of defensive buffs, I was able to survive and heal through it all; I'm not even sure I did a majority of the damage in the fight. Not every boss fight victory where I summon help—ash or player—feels that way, if I feel like I still contributed and did well against the boss. But this time did feel unearned because I otherwise did so poorly throughout the latter fight.)
Anyway, if you're interested: Go to the altar of the moon, the south-Liurnia plateau you get access to at the end of Ranni's questline. I think her questline doesn't get shut out by progress at any point so you should still be able to backtrack for it if you haven't yet. In the plateau's NW corner is an evergaol with a bitch of a fight against a black knife assassin. Beat her and you get a spirit ash that absolutely shreds.
Back to the main point, this is what makes me a little torn on the difficulty in ER: it feels harder than ever before, but they also give you so many tools that can make those fights doable or downright easy beyond the usual option of "summon help" (which is still also an option). They even give you plenty of respec tears and upgrade items to, if you really feel like it, level up a new weapon and respec to use it. Like, I can totally give you a build to trivialize Malenia, or even just a particular helper summon. But I also see how that might be less satisfying than being able to overcome any given boss with a certain build through dedication and practice.