My nearly 2 year old has experienced a variety of directed activities and free play since starting at the nursery when she was 8 months old.
We get an update every day on at least 3 of the activities that she's done that day and it all gets recorded in her wee nursery book.
She has taken part in activities including making sensory objects, water play, sand, playing in shaving foam! (one of her favourites), icing biscuits, making displays, making and decorating cards for various things, painting, chalk boards, play dough etc. They also get free play time and enjoy playing with lots of different types of toys and every day they get stories and sing songs.
Even though 18 months is still very young the nursery should be aware of the benefits of everything that your child is doing from developing fine motor skills, language development and social skills.
If you are concerned then ask for time to sit with a member of staff and discuss your child's development at the nursery. If her day at nursery consists entirely of "free play" then the staff should still be observing and have a rough picture of the skills she has and how she is developing overall.
Does your child have a key worker within the nursery or someone that you can speak to in the first instance to ask about the daily routine in the nursery? It may just be that all of the directed activities take place after the parents leave and before the kids are collected.