Hi Sean. Great question and you are right, if you have thyroid problems, cruciferous veggies can cause some added strain to the thyroid. If you have a healthy thyroid, you do not have to worry about it.
There are a ton of nutrients in cruciferous veggies and they are an extremely important part of a healthy diet!
Here are some ideas for new smoothies that aren't too heavy on the cruciferous veggies if you want some variety to your routine.