I played this game after playing its sequel (Flower Witch), though I don't understand shit about the story (or at least, a little bit), I found both games very enjoyable; I'll be honest, I rarely praise H-games not only because of their "nature", but because there are many of them that are too short, that have terrible art or that are mediocre at best.
Flower Fairy isn't that case (nor its sequel); the game's hard, and it requires to learn via trial & error (so yeah, u gotta have a lot of patience), but at the end is worth it, just make sure you play with a controller though, playing with a keyboard almost drove me mad...
Anyway, I liked the art style, the level design and the challenges (despite me sucking at platforming); though, my biggest complaints would be that the game can't be played on fullscreen, that there are little skills to use (unless I missed smth) and that the controls can be a bit clunky, but nothing too serious to make the game unplayable (it's very playable actually).
All in all, I'd give it a 9/10, an enjoyable experience (and a plus if you like futa, if you don't though, then don't bother playing this game as there's only futa on female and female on female content, unless you don't mind ofc).
Edit; another thing I didn't like is that grenades are useless, and the only useful skill is the "flower bloom" attack.
Also, make sure to check the dev's page; https://ci-en.dlsite.com/creator/2411/article, he's making another game of the "Flower" series, if you're interested.