Yeah, harems and ecchi annoy me. They tend to be comedies, and they're almost never funny. A lot of the jokes are tired or are very contrived. A good romance manga isn't hard to make. A lot of these romance artists are just not very good storytellers. Either that, or they were forced to make romances while they'd rather make something else. I don't know the exact reasons for the lack of quality story-telling other than that works with these cliches go over well with fans, so that shows what I know.
From what I've seen, a romance really works if you have the couple have truly meaningful conversations. Show them being there for each other and proving their mutual respect and loyalty as friends first. After that, allow them to confess without any of the nonsense that usually happens, such as the cat catching their tongue, or ridiculously contrived interruptions or mystifying misunderstandings. All that stuff can ruin an otherwise good series. Kimi ni Todoke is a great example of a great manga turned terrible by having awesome build-up to a pay-off that took forever to happen due to misunderstandings, interruptions and a bunch of other nonsense. By the time the confession did happen, it wasn't worth it.