Puppies from rescues/shelters can be great, if you're willing to take on any size dog. My dad's puppy was supposed to be medium, he is extra large. My friends was meant to be large, it's a small medium.

Getting an adult dog is taking a big risk. I would say out of all the people I know with rescue adults, around 50% of them have to be re-surrendered due to behavioural issues. One of my friends got one that killed the neighbours cat within a week, the shelter wouldn't listen to their concerns and told them he's just settling in. They got a big fine from council, dog put down for being dangerous and are now on the pet owner black list and can't register another dog with council or get any shelter dog and if a breeder checks the list, the will not sell to them. Another friend got a dog that would apparently be fine with low fencing but it wasn't so it had to go back (renters, can't change fencing) and the list could go on.

Generally speaking, I would advise people who are renting or are full time workers to avoid rescuing adult dogs.

If "adopt don't shop" was so simple, more people would do it. But let's be real, a lot of those dogs aren't suitable for most dog owners.