Round baseplates can be made with a lot of small 1xN bricks, made into a rounded corner.
Making things in Blockland is about innovation and working with the bricks you have, not deciding "I need a 8x3F plate, a 10x2x10 wall and a round baseplate" then making them just for one purpose or one build, where they would be useless in others.
I would like more or larger round bricks, though. Maybe a taller and buildable
cone brick or a
4x4x1 Round