Those plastic gears are one of the reasons I love vintage (pre 1960) sewing machines.
Someone once gave me an almost new Singer and it lasted less than a year-plastic gear broke.
I have Kenmore 8 stitch that will probably never break, and a little Singer Spartan that can sew anything and is my main quilt piecing machine as it sews straight stitches very well. Both of them only need a bit of cleaning and oiling to keep running well.
All-metal gears and parts make good sense on a sewing machine.