It really depends on the store and the management of the aquariums. We have pretty good ones almost all the time. Sometimes there are bad weeks or times when the fish look awful and I would just not buy anything iffy unless you have a quarantine tank and plant to use it.
1.5 weeks ago I just bought 13 Pygmy Cories from the local 2 big box stores in different towns nearby me, and one died on the way home but the rest were great. Still looking tiny and cute in QT. Along with 3 Guppies, one died the next day. Other 2 looking good.
A month ago I bought a dozen Chili Rasboras from a really good lfs and all died in QT within 5 days. (cycled and nicely running tank)
Never buy a fish from a group where there are bad looking ones in the tank. Safer than sorry.
Also know the day the fish come in shipments to the store. Usually wait one or 2 days and see what they have living and recovered/ made it through from the shipping process. It is very stressful on the fish.