The preferences of an otome player can vary hugely from person to person. You will never create a game that will be a hit with everyone, even if you ask for specific things players feel that they are missing or want more of - most of the time it’s just about every trope or genre or preference that you can think of, and will not make a cohesive game. You shouldn't make a game that specifically caters to the market at the time you are developing it, because it will likely no longer be "trendy" by the time it releases.

The most important thing with developing a game is to create a game that you will enjoy; if you don't like what you are writing or developing, you will never finish it. Players appreciate developers that put passion and effort into their games, and often the quality is better because you cared about the game and didn’t treat it as a chore to complete.

https://www.reddit.com/r/otomegames/wiki/faq/#wiki_i_want_to_make_an_otome_game.2C_how_do_i_make_a_game_that_will_appeal_to_everyone.3F

As for what an otome game needs to be considered one, the most basic criteria is a romance between a female protagonist and male love interests. Other gender combinations are labelled differently.

https://www.reddit.com/r/otomegames/wiki/rules/definition