Minimalist, I like the handle and I have no problem with you following thru with that approach in your reviews.
Any review is better than nothing.
Things that we appreciate are the same things you might find helpful.
Spa, is it clean, well run, comfortable, cold, warm. Us old men might what to spend an active hour with some beautiful woman but we may not want to climb a set of stairs to get to heaven.
Provider, name, looks, smell, communication skills, demeanor are all good information.
Service, what did you do and how did you like it. you don't have to spell out the gritty details, but adding the two thumbs up symbol to the review will convey that you had a great time.
Lastly, practice makes perfect, so keep writing reviews and they will become better as you write more of them.