Definitely agree with the first point here. The second point I agree with to the extent that it's wrong if you're trying to create a story that other people want to read. If you're just telling the story to yourself or doing it to explore ideas, there is absolutely nothing wrong with it. Just don't expect others to be able to see or agree with where you take the story.
RL doesn't revolve around you and while it is unfair for the author and some readers not being able to get that kind of high, it is more important to try and make a reasonable story.
Hard disagree on this as a general rule. It's important for an author who wants to get published and build a fanbase. For someone who just wants to have fun and write as a hobby, it's important to be unreasonable and see what clicks with you. After finding that, you can worry about being reasonable. Until that point though, trying to make a reasonable story will lead to you falling back on dry tropes, reader opinions, and overall a stiff story.
Also hard disagree on the first thought, but that's a value judgment, so I'll leave it at that.
For a while, I jumped on the bandwagon that everyone was pushing. "Ew, that's a Mary Sue, self-inserts are the worst." I didn't really think about it, since most of my interest in Fantasy is world-building and magic/monster lore.
When I did think about it, it became obvious that it was a mostly subjective thing backed up by a little bit of bad writing. There's a lot of reasons why you might hate an author's self insert character. And I'll probably still say I don't like those things when I spot them.
But, it's possible to write an interesting story where the character is a self-insert; either for the author, or for the reader. I'm too tired to go into detail right now, lol.
The thing is, there's this guy at a manga site that I always frequent (you probably know who he is if you went to mangapark long enough). He just LOVES dissing on these supposedly self-insert isekai harem stories. He would find one, gives it half a star, then copy paste the same crappy review of "OP MC getting a harem, blah blah blah". He's the very reason I asked the question onthe post.
Before I became a writer, all I thought then I saw his "reviews" is that "man, he must be very bored". After I became a writer myself, however, I started to hate on guys like him who just starts crapping on others' hard work without giving a proper criticism.
Alright, I've slept, and I've seen your second comment. First things first, it's completely unrelated to the question you asked. Some people just like to pick fights or talk shit even knowing there's no substance to it. There's people like that everywhere, even on SH. Even if you do everything their way and appeal to them with everything you have, they'll still find something to complain about. So, just Ignore them. No sense getting all worked up over idiots, even if it's hard to ground yourself in the heat of the moment.
The OP MC seeking a Harem is a problem, not because it plays on the author and the readers' desires, but because it's used without any thought, with the hope of getting a lot of fame and readers quickly. It's sort of a get-rich-quick scam? They see the popularity of anime that use that formula, and say, "Well, I want to do that too." Either for personal ambition, or just because they loved the formula and want to replicate it. Think DnD's appeals to replicate the LotR fantasy.
In a way, the answer is the same as the ones you've gotten about self inserts anyways. If that's what they want to do, it's fine. If they do a bad job, nobody will read it. Or only people who've never seen the cliché before will read it. If they do a good job, then they'll be copied by a hundred more people and the cycle will continue.
It's funny that they did such a bad job of reviewing that the point was completely missed though. Criticism is a skill, like any other.
Regarding Self-Inserts, my biggest problems with them have already been addressed, happily. The author gives them everything on a silver platter, ignoring other characters and only offering token resistance. That isn't necessarily a bad thing, but it bores me personally. Frankly, it works better in video games. After all, being a character is easier when you can directly control their actions, and directly suffer the consequences for any mistakes.
Some people just like to pick fights or talk shit even knowing there's no substance to it. There's people like that everywhere, even on SH. Even if you do everything their way and appeal to them with everything you have, they'll still find something to complain about. So, just Ignore them. No sense getting all worked up over idiots, even if it's hard to ground yourself in the heat of the moment.