Mine have all loved the kennels we used to use (for over 25 years) but sadly they have closed down.
I would say it depends on the set up being right for your dog and careful introductions. Mine were all able to just go for a walk around and have a fuss and a treat from the owner and kennel hands on their first visit. We were then able to leave them for just an hour, then an afternoon, then an evening plus overnight, so they got used to it gradually.
It was also privately owned with the owners living on site. Some kennels don’t have staff on site overnight, which is madness to me.
Another important factor was that they owned all the land the dogs were walked on, all of it was securely double fenced and they also had secure paddocks for those that couldn’t go for walks. (I visited kennels once to find all the dogs being walked in big groups by one tiny teenager along a country road and over a motorway bridge to be walked in local fields!)
There was a quiet block for dogs that could be overwhelmed by barking and some kennels were positioned so that the dogs couldn’t see into other kennels if it might agitate the occupants.
Couldn’t have been a more perfect set-up as far as kennels go really and we were so sad when they finally retired and closed the business. My dogs used to drag us into the kennels they were so excited to be there.
We have looked at quite a few other kennels locally since they shut down and nothing even comes close. We now have a family friend who is a professional dog-sitter and they stay in our home to look after our dogs.