What do very thin branches mean are they weak plants ?
Certified GKH Gardening Expert
Most of the time, with clematis, the flowering stems and leaf stems will be very thin and spindly. This is the nature of the plant. They will need to be trellised, or led to climb on something in order to hold itself up.
I do not feel that there is anything wrong with the plant, but if you would like to send photos, then it can help me to see exactly what is going on.
This article will give you more information on growing clematis: https://www.gardeningknowhow.com/ornamental/vines/clematis/growing-clematis.htm