Lol, there are so many things that I dislike or outright hate about irises that it's somewhat bemusing that I grow them at all, never mind have as many as I do.
I hate their relatively low budcount (compared to daylilies).
I hate that the SDBs, IBs, and BBs have even fewer buds than the TBs.
I hate their relatively short period of bloom (again, compared to daylilies... 2 weeks vs 5 weeks minimum). Irises that have "show stalks" of 3 blooms open at once are the worst, because as garden plants they are the worst (the bloom period is over too quickly).
I think rhizomes are ugly. (Sorry, but they are.) I hate that I can't cover the bearded iris rhizomes up with mulch or something, so that I don't have to look at them.
I hate having to constantly clean up dead foliage (a trait shared by daylilies), and I hate it worse that the drier the dead foliage, the harder it is to tear off. (Once a leaf starts yellowing at the tip and heading downwards, I now pull it off, to save myself trouble later.)
I hate muddy color (mostly noticeable in "orange" and "red" irises). (Some daylilies are muddy too. I hate muddy color in anything.)
I hate brown irises specifically. (Mud.)
While I am generally in favor of fragrance, the stronger the better, I hate the sickly-musky smell of some irises.
I hate rebloomers that don't rebloom, or else try to do so in the winter.
I hate that rebloomers generally aren't as advanced in form or color patterns as the spring-only blooming irises.
I hate irises whose stalks fall over.
I hate TBs that are shorter (even though their stalks *don't* fall over).
I hate smaller flowers on TBs.
I hate that irises are seemingly so sensitive to crowding that it turns off their bloom, necessitating frequent division (at least, if they are pot grown).
While I like Space Agers, I hate it when the blooms are not consistent in form (they can't decide if they want to form horns, spoons, or flounces).
I think that's enough to start with.
(It's maybe a good thing I didn't get outdoors today... I might have been kicking more irises out the door.)