Hahaha I'm the same, harems typically aren't my cup of tea.
I know it sounds a little bashy since web novels have a ton of harem stories. It should be judged on a different standard compared to average published novels. We all have different likes and interests and a lot of readers enjoy harems. I don't agree with them but I understand where some readers/writers are coming from.
We also can't ignore the cultural difference in Eastern translated novels. It hasn't been too long since the days a rich powerful official could have 1 official wife and many other wives+concubines. It's everywhere in television dramas and cultural poems/history.
Don't get me wrong OP I completely agree with all your points.
Since web novels are read and written for fun I think most people like to live a little more loosely in enjoying them. It's a self indulgent fantasy for everyone involved. I think at the core a of harem represents the idea of "popularity" . A lot of people wish to be popular, well loved and thought highly of in the minds of others. It's not only a petty innocent ego boost but a sense of validation of your own self worth.
The sad thing here is how society has made people equate their own sense of self worth/self esteem into how popular you are. For both girls and guys, to be well desired by many is supposed to be a brag worthy thing. As if it's a personal accomplishment.
Even the harems stories I do like to read, where the MC and ML are devoted to one another, are not fully exempt from this. Both must be 'popular', even more so than the other characters. The best way to show that is apparently to have a kind of 'quality' harem throwing themselves at the leads.
Generic stallion novels are of course the worst representation of this harem trope. (How many 1 in millions breathtakingly beautiful goddesses can one guy collect? are they common cabbages in their world? are they Pokemon?)