Certified GKH Gardening Expert
These are more than likely fungus gnats. They are harmless, and actually contribute to your plants health to some degree. They only eat dead or rotting material in the soil.
They actually prefer to be in the soil, and not out flying around. They usually only do this when the soil remains too wet for too long. Just make sure that you only water once the top of the soil has dried almost completely.
If you still want to get rid of them, then putting a little rosemary oil, and garlic extract in the water you water with next time.
Here is an article on the proper maintenance of these shrubs: https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/how-to-care-for-hibiscus-plants.htm