Worst two things about your average garbage rom-com with male protagonist are:
1) He's really average or below average looking man with little to no redeeming qualities.
And yet for some reason every woman within 10 kilometers wants him, and is willing to go incredibly degrading lengths to make that happen, regardless of what their characterization should be, based on their age / education level / general personality.
It's way worse than reverse of this is in shoujo, there the worst problem is that all men are "perfect", more like gods than real people.
2) Harem aspect. Women may compete for a guy, but most of the time it stays unnaturally civil, and often even the most jealous woman will end up being happy to share with other competitors, even though none of them is getting any real satisfaction or attention from him. Nobody ever walks away from the competition either in anger after feeling rejected. They all stay in the plot, and sometimes are still after this nobody even when he managed to force himself to "choose one".
Yuri harems are rare, and usually lampoon the concept or make it seem more plausible. Like "She Gets Girls Every Day", where the protagonist is incredibly attractive and sweet girl, who arguably really could charm every non-straight woman she meets.
What's a yuri harem anyway? Off the top of my head I don't remember that many. I can think of two that are updated regularly and I follow: Asumi is interested in Lesbian Brothels and Sorry I'm not Into Yuri. In the 1st one Asumi PAYS those girls to go on dates with her and have sex, arguably she's such a sweetheart she could charm them but not many seem to be seriously smitten with her. In the 2nd one the protagonist is a cute girl with a horrible personality (she's like the lead of a mainstream rom-com in her total lack of redeeming qualities) and she does have a female harem... but only after she drugged all those girls with a love potion! So yeah, the authors make a point of making it plausible.