i dont think its a skill thing here unless you are actually drawing those shapes.
usually when a circle isnt round, theres 2 common issues.
1 is that the machine has backlash. youll see this as a flat spot on 2 opposing sides of a circle.
2 is mach 3 is the drive isnt getting "slow" steps. this is common in some gecko drives. the result is that when an axis is going slow, it doesnt move. the result in a circle is again flat spots on the sides, basically making a squared off circle.
what you are showing is not matching up to the 2 possibilities above.
so you need to look at other things. if everything is tight, and nothing is moving as you cut, then its really coming down to the servos as the next thing to test. given the history with these motors creating wobbly curves when they were first being set up, this is highly likely to be the issue.
so, first run the program 3-4 times to see if the result is the same each time. then try a different tuning setting, different speed, etc, see if changes. if theres a change, you know straight away its the motors. it will save alot of grief finding that our first.
you need to be methodical with issues like this, or youll get nowhere.