The Danger of Extremes in Phenotypes
In the case of selection toward extreme examples of hardiness, disease resistance, fertility or adaptability to varied climate/environmental conditions, we would not be seeing something dangerous to the genus, usually. However, when the selection for extremes in daylilies specifically involves larger and larger flowers without the plant underneath them to support them, wider edges with bigger and bigger bubbles/teeth/ruffles that open poorly, pretty faces regardless of the plant qualities, tall/weak scapes that can't support more than one giant flower open at a time (if even the one), extreme flowers that cannot perform in average garden conditions and require ideal conditions or greenhouses to fully express there phenotypes, pretty faces that are not fertile, and plants that are weak in general, that cannot tolerate real-world conditions or have no resistance to diverse conditions including stress factors such as drought, heat, cold or disease, then the extremes can be creating a two-fold danger.
The first of these dangers is that we are creating a weaker plant that cannot thrive (or perhaps even survive) in a real-world garden, thus loosing the public interest. The second danger is the erosion of the genome of many lines that could potentially bottleneck into a dead-end due to health and/or fertility issues, leaving us with only vegetative reproduction (where such plants are able to increase enough to even be multiplied) without any hope of continued sexual reproduction and thus, no hope of new cultivars from those lines.
While what I am proposing here may seem extreme (and we are admittedly not yet at the precipice), and many may see this as only fear-mongering, all we need to do is look at the history of some of the other domestic lines of animals and plants that have been selected for extremes for a long period of time to see such negative potentials made manifest. There are many examples in the animal world and plant world of domestics that have been selected out of existence or to the brink of existence through a focus on extremes at the cost of survivability/reproducibility.
While I am not suggesting that everyone should start breeding for extremes of hardiness or resistance, I would suggest that keeping hardiness and plant qualities in the back of your mind, at all times, is a good exercise for all plant breeders. It certainly can't hurt, and maybe it will help. Maybe, the next time you have a wonderfully pretty face on a poor plant, instead of introducing it, you could just save it for use as a breeder and work to bring its lovely traits onto a better plant? I know many good breeders already do this. Good breeding requires patience, and all good things come to those who wait. While it has been suggested that patience is the reward of patience, in breeding plants or animals, the reward of patience is often a much better end product.