
You aren't wrong with the braindead power fantasy part however, that was not the end. Despite the female characters fighting over his attention, he didn't requite any of them and at the end, he didn't actually end up with anyone if anyone needs to know. Heck, it got to the point where when that one certain being wanted them all dead, they're all busy surviving there's not even any moment to think about the crushing. Then towards the end, it focused solely on just MC alone and his enemies that it felt like when the other characters are finally on screen again near the ending, it felt rushed like an afterthought.
While some of the females indeed have interest, that was all. The buffer girl is the only one who ended up actually confessing to him, was rejected. Her reaction to finding out his identity made her look unstable in MC's eyes so he made her drink a memory erasure potion without her knowing that's what he made her drink. He erased all her memories and love for him. The lack of consent about that decision over her actually even pissed some readers who rooted for her to be the sole endgame.
In some way, MC once deliberated over how he can't see himself genuinely able to return their feelings because he considers himself too old mentally for having gone though all those regressions. So the option of memory erasure was something of an escape for him too.
Well, fast forward after everything's resolved, the ending had a scene of just the MC and Buffer girl hanging out but no confirmation of being together. At least for now and until side stories are out if anything changes at all.
As for the other guys that ended up dead... Vaguely speaking, they'll be back. Although in a way that guarantees they won't do anything out of line with the acts that made them antagonistic to MC or like Heavenly demon's psychopathic nature truly once deciding to kill the actress and his fiancee.
It's not the best but i'd say it's not actually that bad. ╮( ̄▽ ̄)╭

I was more referring to the fact that any potential competition gets killed off and that literally every girl/woman we meet has a hopeless crush on him.
Even if they don't end up lawfully bound together, i believe it still fits the genre of harem and more importantly gets the point across that female characters are there mostly to make the MC shine.
They are not their own characters, they fulfill functions for the MC to look cool and powerful to insecure boys who are the target demographic of the dungeon regression/towerclimbing/reincarnation genres.
The fact that the MC acknowledges he's too old for them is not really significant as it's often an excuse abandoned halfway ( here it is kinda implied that buffer girl does somehow end up with MC ) and mostly serves the purpose of keeping the door open for more girls to salivate over the harem center.
And honestly it doesn't detract from the fact that any woman/girl he's around loses all independency to rely and swoon over the MC. Which, ultimately, is the problem most people have with these types of harem regardless of the medium : the women are mishandled and end up as non-characters that are passive, helpless and hyper dependent on the MC regardless of how they're supposed to be strong pr smart. The heavenly demon is treated as a possible equal and a threat, he has his own ambitions and goals : he is a real character. The girls's ambitions are get married/help MC/fall in love/protect MC. All their personalities are directly tied to how much they love MC.
Hey so i checked out the novel and it absolutely turns into brain dead power fantasy with ''somehow'' only female characters surviving and being in love and fighting over the MC's attention... So sad i was looking forward to it :(