Well, if you can't make a circle in GIMP, then you have quite a lot to learn. I just asked my kid who's 7, and she easily makes a circle. She would like to show me all the shapes she makes in a minute or two... When I asked her, she made a square, rectangle, triangle, drop, circle, star, lightning, oval, cros and a few more, where she named them all... She had fun doing it, so thanks for that... But please, go practice. BTW I like Krita too - I just don't feel the need to blame any tool for being different from another. :-)
Can I ask you... how often do you really draw a circle, for this to be an issue?
Here's a little guide. My daughter uses the selection tool, to make a lot of shapes... ;-)