use a pair of the thin nitrile/rubber gloves (similar to what mechanics etc use)
Wet your hands, and you will not damage the slime.
It is the same for many of the freshwater fish, and using wet hands reduces the damage.
Some of the large carp in our lakes are caught a few times a year, and some of them are over 60 years old, so not all fish suffer, it is a matter of handling with a bit of care.
Also if you are worried about damage to the fish, squeeze flat the barb on the hook to make it barbless, and as long as you keep the pressure on the fish, it will not come off normally. You may loose maybe 5% that you might otherwise land, but the unhooking is then a doddle.
As for putting the tiddlers back, I have seen on TV how they catch mackerel, and they scoop up hundereds of tonnes in a go, and suck them up by pump. You cant tell me they put the little unes back alive surely, after they have been through all that????