Floral dresses get written off as a bit safe, a bit bridesmaid, the thing your mother in law buys you for a christening. I used to think that too, until I found one that fit properly, and then I understood why they never actually go away.
The thing to watch is what you put them up against. A busy floral clashes badly with another pattern in the same outfit, obviously, but it also fights with anything too fussy at the accessory end, a heavily embellished bag, a statement necklace sitting on top of a print that's already doing plenty of work. Chunky gold jewellery tends to look like an afterthought next to a soft, watercolour print, where something simpler, a thin chain or nothing at all, lets the dress be the whole point. Trainers can go either way depending on the florals, but a stiff, structured sandal with ankle straps often looks like it wandered in from a different outfit entirely. On colour, I've learned to be wary of anything on a white or pale background, because it shows every mark and somehow always looks slightly less expensive than the same print on navy, black or a deep green ground. Those darker grounds also forgive more, which matters if you're the sort of person who eats lunch in whatever you're wearing.
Fit is where florals either earn their keep or sit in the back of the rail for a year. Check where the waist seam actually lands before you buy, not where the model is wearing it pulled up for the photo rail shot, because a seam that's an inch too low makes even a nice print look shapeless. Watch the bust too, particularly on wrap styles, where gaping is the main complaint I hear and the main reason a dress that looked lovely in the shop gets worn once and retired. Sleeve length matters more than you'd expect on a floral, since a cap sleeve that cuts across the widest part of the arm reads very differently to one that sits an inch lower. A well made one tells you straight away, a fabric with proper weight and a bit of drape rather than something thin enough to see knickers through, a print lined up at the seams instead of a flower cut in half at the side, a hem that's been turned and stitched rather than just overlocked and left. The disappointing ones are usually given away by a print that's gone slightly off register, which nobody notices until they're standing in daylight.
Wash on a cool setting and skip the tumble dryer, since heat is what takes a good floral from crisp to crumpled faster than anything else.