I don't know about the particular models you mention but I have a 7-8 year old Janome Memorycraft that was purchased to replace my late 70's Kenmore. I found the Janome intimidating and it sat in the box in a closet for several years. If I needed to sew something, I'd get out the old Kenmore, which functioned similarly to the Singer I'd learned on as a youngster.
I recently got out the "new" Janome during the current lock down and decided I was going to master it or go down trying. It has so many features, stitches and capabilities I'll never use. Too many, I overbought. But I'm taking my time, learning the machine and actually having fun with it. I've just completed two dresses for my dgd. The built in needle threader is awesome for my tired, old eyes!
I googled the Janome J3-24 and it looks like a nice sewing machine. It has more than enough stitches and features and doesn't look intimidating. I'd trade mine for it!
That said, I do think I'll follow the advice given above and have my old Kenmore serviced. The tension occasionally acts up but I'm comfortable with the machine and nothing beats it for a basic, smooth sewing session.